Compliant seal structures for protected active metal anodes

ABSTRACT

Protected anode architectures have ionically conductive protective membrane architectures that, in conjunction with compliant seal structures and anode backplanes, effectively enclose an active metal anode inside the interior of an anode compartment. This enclosure prevents the active metal from deleterious reaction with the environment external to the anode compartment, which may include aqueous, ambient moisture, and/or other materials corrosive to the active metal. The compliant seal structures are substantially impervious to anolytes, catholyes, dissolved species in electrolytes, and moisture and compliant to changes in anode volume such that physical continuity between the anode protective architecture and backplane are maintained. The protected anode architectures can be used in arrays of protected anode architectures and battery cells of various configurations incorporating the protected anode architectures or arrays.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/032,564, filed Feb. 15, 2008, titled COMPLIANT SEALSTRUCTURES FOR PROTECTED ACTIVE METAL ANODES, now pending; which is acontinuation-in-part of U.S. patent application Ser. No. 11/501,676,filed Aug. 8, 2006, titled COMPLIANT SEAL STRUCTURES FOR PROTECTEDACTIVE METAL ANODES, now pending; which claims priority to U.S.Provisional Patent Application No. 60/706,886 filed Aug. 9, 2005, titledELASTOMETRIC SEALS FOR PROTECTED ACTIVE METAL ANODES.

This application also claims priority to U.S. Provisional PatentApplication No. 61/109,127 filed Oct. 28, 2008, titled COMPLIANT SEALSTRUCTURES FOR PROTECTED ACTIVE METAL ANODES.

Each of these prior applications is incorporated herein by reference inits entirety and for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to active metal electrochemicaldevices. More particularly, this invention relates to protected anodesarchitectures incorporating compliant seal structures, including singleand double sided protected anodes and arrays of protected anodes, andtheir associated electrochemical cell structures and devices such asbatteries, particularly, active metal/air batteries and activemetal/seawater batteries, and methods for their fabrication.

The low equivalent weight of alkali metals, such as lithium, makes themparticularly attractive as a battery electrode component. Lithiumprovides greater energy per volume than the traditional batterystandards, nickel and cadmium. Unfortunately, no rechargeable lithiummetal batteries have made significant penetration in the market place.

The failure of rechargeable lithium metal batteries is largely due tocell cycling problems. On repeated charge and discharge cycles, lithium“dendrites” gradually grow out from the lithium metal electrode, throughthe electrolyte, and ultimately contact the positive electrode. Thiscauses an internal short circuit in the battery, rendering the batteryunusable after a relatively few cycles. While cycling, lithiumelectrodes may also grow “mossy” deposits that can dislodge from thenegative electrode and thereby reduce the battery's capacity.

To address lithium's poor cycling behavior in liquid electrolytesystems, some researchers have proposed coating the electrolyte facingside of the lithium negative electrode with a “protective layer.” Suchprotective layer must conduct lithium ions, but at the same time preventcontact between the lithium electrode surface and the bulk electrolyte.Many techniques for applying protective layers have not succeeded.

Some contemplated lithium metal protective layers are formed in situ byreaction between lithium metal and compounds in the cell's electrolytethat contact the lithium. Most of these in situ films are grown by acontrolled chemical reaction after the battery is assembled. Generally,such films have a porous morphology allowing some electrolyte topenetrate to the bare lithium metal surface. Thus, they fail toadequately protect the lithium electrode.

Prior work in the present applicants' laboratories has developedtechnology for protecting active metal anodes with highly ionicallyconductive protective membrane architectures. These protected activemetal anodes structures and associated electrochemical cells, describedin applicants' co-pending published US Applications US 2004/0197641 andUS 2005/0175894, and their corresponding International PatentApplications WO 2005/038953 and WO 2005/083829, respectively, representmajor advances in active metal battery technology, for instancerendering possible functional Li/air and Li/water batteries. Thistechnology would be further advanced by the development of sealstructures and techniques that would facilitate and/or optimize theimplementation of these protected active metal anode structures.

SUMMARY OF THE INVENTION

The present invention provides protected anode architectures havingionically conductive protective membrane architectures that, inconjunction with compliant seal structures and anode backplanes,effectively enclose an active metal anode inside the interior of ananode compartment. This enclosure prevents the active metal fromdeleterious reaction with the environment external to the anodecompartment, which may include aqueous, ambient moisture, organic liquidelectrolytes (or catholytes—electrolytes in contact with the cathode,and in some aspects catholyte may also comprise dissolved or suspendedredox active species and redox active liquids), aqueous and non-aqueouscatholytes, redox active liquids such as seawater, oxyhalides such asSOCl₂, dissolved redox species such as transition metal chlorides orbromides, and/or electrochemically active materials corrosive to theactive metal. It also prevents loss of volatile components that may beused in the interior volume of the sealed anode.

During discharge, the active metal mass and volume of the anodedecreases. If this volume decrease is not compensated in some manner,interfacial gaps between the active metal anode and the protectivemembrane architecture could result, leading to reduced ionic contactarea between the active metal anode and protective membrane architecturewith subsequent performance degradation. Similar gaps or voids betweenthe active metal anode and backplane can also degrade performance wherethe backplane is or includes the anode current collector and electricalcommunication between the two is disrupted. If such interfacial gaps andvoid formation in the anode compartment could be reduced or eliminated,enhanced electrochemical performance would result along with a compactcell structure.

The compliant seal structures of the present invention are substantiallyimpervious to anolytes, catholyes, dissolved species in electrolytes,and moisture, and are compliant to changes in anode volume such thatphysical continuity (e.g., ionic, electronic and/or mechanicalcontinuity) between the anode, protective architecture and backplane aremaintained. The volume of the anode compartment changes in directrelationship to changes in the active metal thickness during chargingand discharging of the sealed protected anode and thereby reduces (e.g.,minimizes) the volume (and weight), and increases (e.g., maximizes) theenergy density of a corresponding electrochemical cell structure.

In the context of the present invention, physical continuity correspondsto at least one of ionic continuity, mechanical force continuity andelectronic continuity. For the anode of the present invention to be inphysical continuity with another component, such as the anode backplaneor the protective membrane architecture, it is meant that the anode isat least in one of ionic continuity, mechanical force continuity and/orelectronic continuity with the other component.

By ionic continuity, it is meant that under an associated electric fieldand/or concentration gradient active metal ions are transportablebetween the anode and the protective membrane architecture.

By electronic continuity it is meant that under an associated electricfield electrons are transportable between the anode and the anodebackplane in the instance whereby the anode backplane provides currentcollection for the anode.

By mechanical force continuity it is meant that mechanical force appliedonto or by the anode backplane and/or protective membrane architectureis transmittable to the anode; and mechanical force applied onto or bythe anode is transmittable to the anode backplane and/or protectivemembrane architecture.

In all instances of the invention, the protective ion membranearchitecture is in ionic transport continuity with the anode. It mayalso be in mechanical force continuity with the anode.

In the instances whereby the anode backplane is an insulator, the anodebackplane is in mechanical force continuity with the anode.

In the instances whereby the anode backplane comprises an electronicconductor that provides current collection for the anode, the anodebackplane is in electronic continuity with the anode. In this instance,the anode backplane may also be in mechanical continuity with the anode.

In the instances whereby the anode backplane is a protectivearchitecture, the anode backplane is in ionic continuity with the anode.It may also be in mechanical force continuity with the anode.

The greater the extent and uniformity of the physical continuity, thebetter will be the performance of the protected anode architecture. Lossof physical continuity means that the physical continuity has degradedto such an extent that the protected anode architecture of the presentinvention is no longer functional as an anode.

In one aspect, the invention relates to a protected anode architecture.The protected anode architecture includes an active metal anode having afirst surface and a second surface; an ionically conductive protectivemembrane architecture on the first surface of the anode; an anodebackplane on the second surface of the anode; and a compliant sealstructure interfacing with the protective membrane architecture and theanode backplane to enclose the anode in an anode compartment, the sealstructure being compliant to changes in anode thickness such thatphysical continuity between the anode, protective architecture andbackplane are maintained. The ionically conductive protective membranearchitecture comprises one or more materials configured to provide afirst membrane surface chemically compatible with the active metal ofthe anode in contact with the anode, and a second membrane surfacesubstantially impervious to and chemically compatible with anenvironment exterior to the anode compartment. The compliant sealstructure, the protective membrane architecture and the anode backplaneare interfaced (e.g., bonded, joined or in contiguity) such that asubstantially impervious barrier between the interior and exterior ofthe anode compartment is provided.

In various embodiments the compliant seal structure is, or comprises, aflexible film preformed into a desired shape configuration, typically bypressing and cutting. In certain embodiments that flexible film is amultilayer laminate comprising at least two layers: a top layer opposingthe external environment and a bottom layer opposing the internalenvironment of the anode compartment.

In certain embodiments the multilayer laminate has at least oneadditional layer, a barrier layer, typically a metal foil (e.g., an Alalloy); a bottom layer that is a heat sealable thermoplastic and a toplayer, also a thermoplastic material, with a melt temperature higherthan that of the bottom layer.

In some embodiments the multilayer laminate comprises an inner secondarysealant layer that extrudes, under thermal compression, out the edge ofthe laminate to coat over exposed material layers, thereby protectingthem from contact with the external environment about the anodecompartment, and in particular to protect the edge of the bottom layer.

In other aspects, low temperature performance of the protected anodearchitecture and battery cells of the instant invention may be enhancedin a multilayer laminate compliant seal structure by selecting certainmaterial layers having a glass transition temperature (Tg) that is lowerthan the predefined lower bound operating temperature limit of theprotected anode architecture or the device in which it is incorporated.

When used as a component layer in a compliant seal structure, a low Tgmaterial layer has the advantage that above its glass transitiontemperature it remains in a rubbery state, where it is beneficially mostflexible. Below Tg, its elastic modulus may increase, and the layer maystiffen.

In one embodiment of the invention, the compliant seal structure is amultilayer laminate having an uppermost thermoplastic glass transitiontemperature that is below the predefined low operating temperature limitof the anode architecture, or below the predefined lower bound operatingtemperature of the device in which it is incorporated (e.g., batterycell).

In certain embodiments of the invention, the compliant seal structure isa multilayer laminate wherein no thermoplastic material layer ofthickness greater than 200 microns, or greater than 100 microns, or 50microns or 20 microns or greater than 10 microns or greater than 5microns has a glass transition temperature above the lower boundoperating temperature of the protected anode architecture or that of thedevice in which it is incorporated.

In some embodiments the Tg of the top and bottom thermoplastic materiallayers of a multilayer laminate compliant seal structure is below thelower bound operating temperature of the protected anode architecture ordevice thereof. That is, neither layer (top or bottom) has a glasstransition temperature greater than the lower bound operatingtemperature limit.

In various embodiments, particularly suitable thermoplastic materiallayers for use in a multilayer compliant seal structure of a protectedanode architecture of the instant invention and battery cell thereof,and which is intended for operation inclusive of low temperature, arepolymer layers (thermoplastic layers) having a glass transitiontemperature that is below room temperature (i.e., below about 15° C.),and preferably below 10° C., below 5° C., below 0° C., or below −5° C.,and even below −10° C., below −20° C., below −30° C., and below −40° C.,depending upon the desired operation temperature.

Arrays of protected anode architectures, battery cells of variousconfigurations incorporating the protected anode architectures orarrays, and methods of making them are also provided.

These and other features of the invention will be further described andexemplified in the drawings and detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-E illustrate various views of a protected anode architecture inaccordance with one embodiment of the present invention.

FIGS. 2A-D illustrate various alternative configurations of a protectivemembrane architecture in accordance with the present invention.

FIGS. 3A-H illustrate various alternative configurations of a complaintseal structure for a protected anode architecture in accordance withembodiments of the present invention.

FIGS. 4A-C illustrate a protected anode architecture in accordance withan embodiment of the present invention in which the protected anode hasa double-sided protected anode structure.

FIGS. 5A-C show protected anode architecture planar array formats inaccordance with embodiments of the present invention.

FIGS. 6A-B show protected anode architecture tubular array formats inaccordance with embodiments of the present invention.

FIG. 7A-B shows a protected anode architecture spiral array formats inaccordance with an embodiment of the present invention.

FIGS. 8A-B illustrates a hub and spoke double-sided protected anodearchitecture array in accordance with an embodiment of the presentinvention.

FIGS. 9A-B show an active metal/air battery cell incorporating aprotected anode architecture in accordance with an embodiment of thepresent invention.

FIG. 10 shows a double-sided active metal/air battery cell incorporatinga protected anode architecture in accordance with an embodiment of thepresent invention.

FIG. 11 shows another metal/air battery cell design incorporating aprotected anode architecture in accordance with an embodiment of thepresent invention.

FIGS. 12A-B depict embodiments of metal/seawater cells with protectedanode architectures in accordance with the present invention.

FIG. 13 illustrates a cross sectional depiction of a generalelectrochemical cell structure in accordance with the present invention.

FIG. 14 depicts an embodiment of a double-sided, asymmetric, protectedanode architecture in accordance with the present invention.

FIGS. 15A-C depict an embodiment of a metal/seawater cell battery with aprotected anode architecture in accordance with the present invention.

FIG. 16 depicts a plot of the discharge curve of the test cell ofExample 2 incorporating a protected anode architecture having acompliant seal structure in accordance with the present invention.

FIGS. 17A-B illustrates the shape and configuration of a multi-layerlaminate compliant seal structure of Example 3 in accordance with thepresent invention.

FIG. 18 depicts a plot of the discharge curve of the test cell ofExample 3 incorporating a protected anode architecture having acompliant seal structure in accordance with the present invention.

FIG. 19 depicts a plot of the discharge curve of the test cell ofExample 4 containing aqueous metal/air cell electrolyte andincorporating a double-sided protected anode architecture having acompliant seal structure in accordance with the present invention.

FIG. 20 depicts a plot of the discharge curve of test cell of Example 5containing seawater as electrolyte and incorporating a double-sidedprotected anode architecture having a compliant seal structure inaccordance with the present invention.

FIGS. 21A-C illustrate the shape and configuration of multi-layerlaminate compliant seal structure of Example 6 in accordance with thepresent invention.

FIG. 22 depicts a plot of the discharge curve of the test cell ofExample 7 containing seawater as electrolyte and incorporating adouble-sided protected anode architecture having an asymmetric compliantseal structure in accordance with the present invention.

FIG. 23 depicts a plot of the discharge curve of the test cell ofExample 8 incorporating a double-sided protected anode architecturehaving an asymmetric compliant seal structure in accordance with thepresent invention.

FIGS. 24A-D illustrate schematically in cross section (A-B) the coveringthe exposed edges of a multilayer laminate compliant seal structure witha discrete sealant, and (C-D) the covering of an exposed edge via theuse of an integrated secondary sealant as a component layer of themultilayer laminate.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In the following description, the invention is presented in terms ofcertain specific compositions, configurations, and processes to helpexplain how it may be practiced. The invention is not limited to thesespecific embodiments. For example, for clarity of presentation, theinvention is described herein primarily with reference to Li-basedanodes. However, it should be understood that suitable anodes may becomposed of other active metals, alloys and intercalating anodes asdescribed herein, and the protective films or reagents described ascontaining Li may correspondingly contain such other active metals oralloys. Examples of specific embodiments of the invention areillustrated in the accompanying drawings. While the invention will bedescribed in conjunction with these specific embodiments, it will beunderstood that it is not intended to limit the invention to suchspecific embodiments. On the contrary, it is intended to coveralternatives, modifications, and equivalents as may be included withinthe scope and equivalents of the invention described herein. In thefollowing description, numerous specific details are set forth in orderto provide a thorough understanding of the present invention. Thepresent invention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail in order to not unnecessarily obscure the presentinvention.

Introduction

The protected anodes of the present invention have ionically conductiveprotective membrane architectures that in conjunction with compliantseal structures of the present invention and anode backplaneseffectively enclose an active metal (e.g., alkali metals like Na and Li)anode inside the interior of an anode compartment. This enclosureprevents the active metal from deleterious reaction with the environmentexternal to the anode compartment, which may include aqueous, ambientmoisture, catholytes (electrolytes in contact with the cathode, and insome aspects catholyte may also comprise dissolved or suspended redoxactive species and redox active liquids), the general cathodeenvironment (cathode compartment) and/or electrochemically activematerials corrosive to the active metal, and it prevents loss ofvolatile components that may be used in the interior volume of thesealed anode.

During discharge, the active metal mass and volume of the anodedecreases; typically manifested as a decrease in active metal thickness.Unless this volume decrease is compensated for in some manner, voidscould be created as interfacial gaps between the active metal anode andthe protective membrane architecture, leading to losses in ionic contactbetween the active metal and protective membrane architecture along withsubsequent performance degradation. Similar voids between the activemetal anode and backplane can also degrade performance where thebackplane is or includes the anode current collector and electricalcontinuity between the two is disrupted. If such interfacial gaps andvoid formation in the anode compartment could be reduced or eliminated,enhanced electrochemical performance would result along with a compactcell structure.

Similarly, internal seals can adversely affect the energy density of abattery cell in that as the battery is discharged, the active metalmaterial thickness decreases (to a limit of zero thickness at 100%discharge for an active metal foil) leaving an internal void in thebattery at the same time that products formed outside the protectedanode compartment, for example in the positive electrode, lead to avolume expansion. As a result, the battery design needs to include extraspace to accommodate that expansion. If the void volume formed in theanode compartment during battery discharge could be used to accommodatethe positive electrode expansion, a compact cell design would result,and a higher energy density as well. The use of a conventional sealprecludes capture of the liberated anode volume.

The compliant seal structures of the present invention are substantiallyimpervious to anolytes, catholyes, dissolved species in electrolytes,and moisture and compliant to changes in anode volume such that physicalcontinuity between the anode protective architecture and backplane aremaintained. The protective membrane architecture comprises asubstantially impervious solid electrolyte membrane that provides activemetal ion transport while effectively blocking transport of liquids andgases; in this way the active metal is protected from the deleteriouseffects of ingress of air or water, and prevents loss of volatilecomponents which may be used adjacent to the active metal surface. Inorder to form an enclosed anode compartment that effectivelyencapsulates the active metal anode, the perimeter of the solidelectrolyte is sealed by compliant seal structures of the instantinvention which are substantially impervious to liquids and gases and inconjunction with the protective membrane architectures and anodebackplanes fully enclose an anode compartment.

The protected anode architecture prevents loss of effective functionalcontact (providing ionic communication) of the active metal of the anodewith the protective membrane architecture by virtue of the compliantnature of the compliant seal. The seal conforms to volume changes in theanode compartment during cycling as the active anode material (e.g.,lithium) is exhausted on discharge or regenerated on charge, and enablesthe protected anode compartment to adjust to pressure and volume changesthat take place both within and external to the anode compartment. Thecompliant seal structure also serves to minimize volume of the anodecompartment and thereby reduce (e.g., minimize) the volume (and weight)and increase (e.g., maximize) the energy density of the correspondingelectrochemical cell structure (e.g., battery cell).

The protected anode architectures with compliant seal structures of theinstant invention have particular utility in metal air batteries such asLi/air or Na/air batteries. In the galvanic Li/Air cell, for example,the negative electrode supplies a source of lithium to the reaction,physically manifested by the disappearance of the lithium metal foil,concomitant with the production of lithium hydroxide at the positiveelectrode. In the Li-Air cell, the product LiOH is stored in an aqueouscatholyte reservoir, leading to an expansion of positive electrodevolume with proceeding cell discharge. As the discharge progresses, thepresence of the compliant seal structure allows the expansion of thepositive electrode volume to be compensated by the decrease in volume ofthe negative electrode.

The protected anode architectures with compliant seal structures of theinstant invention also yield significant benefit for metal/seawaterbatteries including Li/seawater (or Na/seawater). Such batteries haveexceptionally high energy density (Wh/l) and specific energy (Wh/kg)since seawater serves as both the aqueous electrolyte and oxidant, anddoes not have to be carried in the battery pack. The use of flexibleseals to enclose the protected anode compartment allows the hydrostaticpressure of the ocean to compress the anode compartment as discharge ofthe negative electrode proceeds, facilitating uniform pressure of thesolid electrolyte plate against the active metal of the anode which isimportant to achieve full utilization of the active metal.

The present invention also encompasses arrays of protected anodes orcells. In particular, the compliant seal structures of the instantinvention allow for flexible anode arrays with varying degrees of jointflexibility, and both rigid and flexible arrays having a wide variety ofgeometric configurations, including the ability to be assembled ontoand/or conform to various structural shapes and forms. A number ofconfigurations for the protective membrane architecture and theirassociated electrochemical structures are enabled by the anode arrays ofthe present invention including tubular arrays of cells, arraysconformed to the surface of regular or irregularly shaped bodies andspiral-type configurations. While the present invention enablesprotected anode arrays that are rigid, flexibility may add ruggednessespecially in the case of large area protective membrane architectureswhere significant benefits in terms of handling during manufacture andimplementation may be gained.

The ionically conductive protective membrane architectures described incommonly-owned co-pending published US Applications US 2004/0197641 andUS 2005/0175894, in combination with the compliant seal structures ofthe present invention, isolate the active metal anode from itssurrounding environment, such that the active metal anode and thecomponents in the interior of the anode compartment are not in contactwith ambient moisture or battery cell components such as aprotic oraqueous catholytes. This is in contrast to conventional active metalbatteries, such as lithium metal batteries where the lithium metal foil,microporous separator (e.g., Celgard) and positive electrode are all inintimate contact with the organic aprotic solvent in the liquidelectrolyte. The compliant seal structures of the present inventionprovide a substantially impervious, chemically resistant barrier thatencloses the entirety of the protected anode compartment and alsoprovide a mechanical framework to maintain a gap free interface and acompact structure that minimizes wasted volume and weight and maximizesenergy density and specific energy.

Protected Anode Architecture

The protected anode architectures of the present invention comprise anactive metal anode, an ionically conductive protective membranearchitecture, an anode backplane, and a compliant seal structure, thatwhen joined together effectively form an hermetic anode compartment thatencloses the active metal anode. The protected anode architectureprovides active metal ion transport into and out of the anodecompartment via the protective membrane architecture and can beconfigured to provide an electronic current transport into and out ofthe anode compartment via an electronically conductive backplane orother terminal contact. The anode compartment of the present inventionis substantially impervious to anolytes, catholyes, dissolved species inelectrolytes, and moisture; and by virtue of its compliant sealstructure is compliant to changes in anode volume such that physicalcontinuity (e.g., ionic, electronic and mechanical continuity) betweenthe anode, protective architecture and backplane are maintained.

In the context of the present invention, physical continuity correspondsto at least one of ionic continuity, mechanical force continuity andelectronic continuity. For the anode of the present invention to be inphysical continuity with another component, such as the anode backplaneor the protective membrane architecture, it is meant that the anode isat least in one of ionic continuity, mechanical force continuity and/orelectronic continuity with the other component.

By ionic continuity, it is meant that under an associated electric fieldand/or concentration gradient active metal ions are transportablebetween the anode and the protective membrane architecture.

By electronic continuity it is meant that under an associated electricfield electrons are transportable between the anode and the anodebackplane in the instance whereby the anode backplane provides currentcollection for the anode.

By mechanical force continuity it is meant that mechanical force appliedonto or by the anode backplane and/or protective membrane architectureis transmittable to the anode; and mechanical force applied onto or bythe anode is transmittable to the anode backplane and/or protectivemembrane architecture.

In all instances of the invention, the protective membrane architectureis in ionic transport continuity with anode. It may also be inmechanical force continuity with the anode.

In the instances whereby the anode backplane is an insulator, the anodebackplane is in mechanical force continuity with the anode.

In the instances whereby the anode backplane comprises an electronicconductor that provides current collection for the anode, the anodebackplane is in electronic continuity with the anode. In this instance,the anode backplane may also be in mechanical continuity with the anode.

In the instances whereby the anode backplane is a protective membranearchitecture, the anode backplane is in ionic continuity with the anode.It may also be in mechanical force continuity with the anode.

The greater the extent and uniformity of the physical continuity, thebetter will be the performance of the protected anode architecture. Lossof physical continuity means that the physical continuity has degradedto such an extent that the protected anode architecture of the presentinvention is no longer functional as an anode.

Basic components of the protected anode architecture include:

i) an active metal anode having a first and second surface;

ii) an ionically conductive protective membrane architecture that issubstantially impervious and encapsulates the first surface of theactive metal anode while providing active metal ion transport; iii) ananode backplane that is substantially impervious and encapsulates thesecond surface of the active metal anode; and

iv) a compliant seal structure, that is substantially impervious andjoins, by a seal, the protective membrane architecture to the anodebackplane while allowing the anode compartment to alter its volume(essentially by changes in thickness) during charge and discharge.

In order to extract electrical current from the anode, an electronicallyconductive member in electronic continuity with the active metal anodeand extending outside the anode compartment is also required. This canbe provided by an anode backplane that is electronically conductive orhas an electronically conductive component in contact with the anodeactive material, or by a separate electronically conductive terminalconnector in contact with the anode active material.

The protected anode architecture of the present invention is describedbelow in more detail and this is followed by further detaileddescriptions of specific embodiments including those of protectedanodes, arrays of protected anodes and electrochemical cells such asthose using aqueous electrolytes or other electrolytes that wouldotherwise adversely react with the active metal material of the anode ifnot for the hermetic enclosure provided by the anode compartment.

A representative protected anode architecture in accordance with thepresent invention is described with reference to FIGS. 1A-E. It shouldbe understood that the architecture depicted in FIGS. 1A-E is only oneembodiment of the invention, and many variations are possible, asdescribed further below.

Referring to FIG. 1A there is illustrated a perspective view, with acut-away to reveal the various layers, of a stand alone single sided,protected anode architecture 120 comprising an active metal anode 100, aprotective membrane architecture 102, an anode backplane 106, and acompliant seal structure 104. When joined and sealed, the protectivemembrane architecture 102, anode backplane 106, and compliant sealstructure 104 effectively form a hermetic anode compartment thatencloses the active metal anode 100. An optional separate currentcollector 108 disposed between the anode 100 and the backplane 106 andan electronically conductive terminal 110 connected with the currentcollector 108 extends outside the anode compartment through a portalformed at a juncture between the anode backplane 106 and the compliantseal structure 104. In this embodiment, the anode backplane more broadlyincludes backplane support component 107, which may be, for example, abattery cell packing/container material, and the current collector 108and electronically conductive terminal 110. In other embodiments,components 108 and 110 may be a single piece of material (e.g., a coppersheet). Also, support component 107 may be absent where the backplane isa substantially impervious anode current collector; and in this instancecomponent 110 may also be unnecessary.

The protected anode architecture is hermetic in the sense that the anodecompartment is substantially impervious, as defined above, to itsexternal environment, and internal volatile components are preventedfrom escaping to the external environment. By substantially imperviousit is meant that the material provides a sufficient barrier toconstituents of the external environment, such as moisture, aqueous andnon-aqueous catholytes, constituents from the cathode environment(cathode compartment) including redox active species and solvents andother active metal corrosive battery component materials that would bedamaging to the active metal anode material, to prevent any such damagethat would degrade electrode performance from occurring. Thus, it shouldbe non-swellable and free of pores, defects, and any pathways allowingmoisture, electrolyte, catholyte etc. to penetrate through it. It alsoprovides a substantially impervious barrier to components, includingvolatile anolyte solvents, inside the anode compartment from escaping,to prevent any such damage that would degrade electrode performance fromoccurring. The protected anode architecture also provides active metalion transport into and out of the anode compartment via the protectivemembrane architecture and for passage of electronic current to and fromthe active metal anode to the exterior of the anode compartment by meansof an current collector/electronically conductive terminal that may beor be incorporated in the anode backplane.

Referring to FIG. 1B, a cross-sectional view of the protected anodearchitecture of FIG. 1A is shown in the charged state. The active metalanode 100 has a first and second surface. The first surface is adjacentto the ionically conductive protective membrane architecture 102 and thesecond surface is adjacent to the anode backplane 106. An optionalcurrent collector 108 is bonded to the active metal anode. Asubstantially impervious compliant seal structure 104 provides thesurrounding enclosure for the active metal anode 100 and is joined, by aseal, to the protective membrane architecture 104 and the anodebackplane 106, which serve to encapsulate the first and second surfaceof the active metal anode 100, respectively. The electronicallyconductive terminal 110 is in direct contact with the current collector108; accordingly, it is also in electronic continuity with the activemetal anode 100. The electronically conductive terminal 110 extendsoutside the anode compartment through a portal formed at a juncturebetween the anode backplane and the compliant seal structure.

FIG. 1C depicts a cross-sectional view of the protected anodearchitecture of FIG. 1B in a discharged state, which helps to illustratea substantial benefit of the compliant seal structure. As it isdischarged, the anode 100 loses mass and volume. The protected anodearchitecture 120 is able to accommodate the loss of anode volume withthe compliant seal structure 104 flexing as the gap between theprotective membrane architecture 102 and the anode backplane 106narrows. In this way, the anode compartment remains sealed and the anoderemains in ionic and electronic communication with the protectivemembrane and current collector 108 of the backplane 106, respectively.

FIGS. 1D and 1E show top plan views of the protected anode architectureof FIGS. 1A-C, with FIG. 1E showing a cut-away to reveal the variouslayers below the top surface.

Features of the protective anode architecture will now be described inmore detail:

(i) Active Metal Anode

The active metal anode 100 comprises at least one of an active metalmaterial layer, active metal alloy layer, active metal ion layer andactive metal intercalating layer.

Active metals are highly reactive in ambient conditions and can benefitfrom a barrier layer when used as electrodes. They are generally alkalimetals such (e.g., lithium, sodium or potassium), alkaline earth metals(e.g., calcium or magnesium), and/or certain transitional metals (e.g.,zinc), and/or alloys of two or more of these. The following activemetals may be used: alkali metals (e.g., Li, Na, K), alkaline earthmetals (e.g., Ca, Mg, Ba), or binary or ternary alkali metal alloys withCa, Mg, Sn, Ag, Zn, Bi, Al, Cd, Ga, In, Sb. Preferred alloys includelithium aluminum alloys, lithium silicon alloys, lithium tin alloys,lithium silver alloys, and sodium lead alloys (e.g., Na₄Pb). Preferredactive metal electrodes are composed of the alkali metals lithium (Li)or sodium (Na). Li is particularly preferred.

Moreover, in a discharged state, the active metal material layer may bean active metal alloying metal such as aluminum, silicon or tin, or anactive metal intercalating material such as carbon or others well knownin the art. The use of active metal intercalating layers that reversiblyintercalate and de-intercalate active metal ions such as Li ions and Naions provide beneficial characteristics. First of all, it allows theachievement of prolonged cycle life of the battery without the risk offormation of active metal dendrites. Preferred active metalintercalating layers have a potential near that (e.g., within about 1volt) of their corresponding active metal (e.g., Li, Na). A preferredactive metal intercalating layer is carbon, well known to those of skillin the art of Li-ion batteries.

Electrochemical cell structures, such as secondary batteries, thatincorporate a carbon anode greatly benefit from the protected anodearchitectures of the present invention in that the anode is completelyde-coupled from the cathode environment. Accordingly, both anolyte(electrolyte in contact with the anode) and catholye (electrolyte incontact with the cathode) are optimized independently.

As illustrated in FIGS. 1A-E, the active metal anode layer 100 has twomajor surfaces. A first surface that is encapsulated by the protectivemembrane architecture 102 and a second surface opposing that of thefirst and which is encapsulated by the anode backplane 106. In itsvarious embodiments the active metal anode layer generally encompassesthose instances wherein the thickness of the anode layer is greater orless than the length of a line that bisects the face formed by eitherits first or second surfaces. For instance, if the first anode surfaceforms a circular or square face, the length of the bisector is itsdiameter or side length, respectively.

In certain preferred embodiments, the anode layer is in the form of anactive metal layer or active metal alloy layer such as a lithium foil,disc, sheet, cylinder, block or plate, or more generally a body oflithium having two opposing ends and a lateral surface. The surfaces ofthe two ends are generally referred to herein as the first and secondsurface of the anode layer, respectively. Preferably, the first andsecond surfaces of the anode are not only opposing, they are preferablyaligned and parallel with each other. For instance, in variousembodiments the anode body is in the form of a block or cylinder oflithium. A particularly preferred anode is a lithium or sodium metallayer in the form of a right cylinder (e.g., a rod of lithium) or arectangular prism (e.g., a slab of lithium with, for example, squareshaped opposing ends)

Regardless of the geometry of the anode, when configured in a protectedanode architecture, the first surface is encapsulated by a protectivemembrane architecture and the second opposing surface is encapsulated bythe anode backplane. With regard to the height/thickness of the activemetal anode, it is measured as the shortest distance between the firstand second surface.

As noted above, in a preferred embodiment, the active metal material islithium or sodium metal, in particular Li. The active metal materiallayer is at least 10 microns thick, and may be up to 1 cm or more thick.Some preferred thickness ranges are preferably between 10 and 50microns, 50 and 100 microns, 0.1 and 1 mm, 1 mm and 10 mm, 10 mm and 100mm, and 100 mm and 500 mm thick.

(ii) Protective Membrane Architecture

The protective membrane architecture 102 on the first surface of theactive metal anode 100 selectively transports the active metal ions intoand out of the anode compartment while providing an impervious barrierto the environment external to the anode compartment. It also provides abarrier to components inside the anode compartment from escaping.Protective membrane architectures suitable for use in the presentinvention are described in applicants' co-pending published USApplications US 2004/0197641 and US 2005/0175894 and their correspondingInternational Patent Applications WO 2005/038953 and WO 2005/083829,respectively, incorporated by reference herein.

FIGS. 2A-D illustrate representative protective membrane architecturesfrom these disclosures suitable for use in the present invention:

Referring to FIG. 2A, the protective membrane architecture can be amonolithic solid electrolyte 202 that provides ionic transport and ischemically stable to both the active metal anode 201 and the externalenvironment. Examples of such materials are Na-β″ alumina, LiHfPO₄ andNASICON, Nasiglass, Li₅La₃Ta₂O₁₂ and Li₅La₃Nb₂O₁₂. Na₅MSi₄O₁₂ (M: rareearth such as Nd, Dy, Gd)

More commonly, the ion membrane architecture is a composite composed ofat least two components of different materials having different chemicalcompatibility requirements, one chemically compatible with the anodeenvironment in the interior of the anode compartment, the otherchemically compatible with the exterior; generally ambient air or water,and/or battery electrolytes/catholytes. By “chemical compatibility” (or“chemically compatible”) it is meant that the referenced material doesnot react to form a product that is deleterious to battery celloperation when contacted with one or more other referenced battery cellcomponents or manufacturing, handling, storage or external environmentalconditions. The properties of different ionic conductors are combined ina composite material that has the desired properties of high overallionic conductivity and chemical stability towards the anode, the cathodeand ambient conditions encountered in battery manufacturing. Thecomposite is capable of protecting an active metal anode fromdeleterious reaction with other battery components or ambient conditionswhile providing a high level of ionic conductivity to facilitatemanufacture and/or enhance performance of a battery cell in which thecomposite is incorporated.

Referring to FIG. 2B, the protective membrane architecture can be acomposite solid electrolyte 210 composed of discrete layers, whereby thefirst material layer 212 is stable to the active metal anode 201 and thesecond material layer 214 is stable to the external environment.Alternatively, referring to FIG. 2C, the protective membranearchitecture can be a composite solid electrolyte 220 composed of thesame materials, but with a graded transition between the materialsrather than discrete layers.

The low equivalent weight of alkali metals, such as lithium, render themparticularly attractive as a battery electrode component. However,metals such as lithium or sodium or compounds incorporating lithium witha potential near that (e.g., within about a volt) of lithium metal, suchas lithium alloy and lithium-ion (lithium intercalation) anodematerials, are highly reactive to many potentially attractiveelectrolytes and cathode materials. The protective membranearchitectures provide a barrier to isolate an active metal, active metalalloy or active metal ion anode in the anode compartment from ambientand/or the cathode side of the cell while allowing for efficient ionactive metal ion transport into and out of the anode compartment. Thearchitecture may take on several forms. Generally it comprises a solidelectrolyte layer that is substantially impervious, ionically conductiveand chemically compatible with the external ambient (e.g., air or water)or the cathode environment. By chemically compatible it is meant thatthe reference material does not react to form a product that isdeleterious to battery cell operation when contacted with one or moreother referenced battery cell components or manufacturing, handling,storage or external environmental conditions.

Generally, the solid state composite protective membrane architectures(described with reference to FIGS. 2B and C) have a first and secondmaterial layer. The first material layer (or first layer material) ofthe composite is ionically conductive, and chemically compatible with anactive metal electrode material. Chemical compatibility in this aspectof the invention refers both to a material that is chemically stable andtherefore substantially unreactive when contacted with an active metalelectrode material. It may also refer to a material that is chemicallystable with air, to facilitate storage and handling, and reactive whencontacted with an active metal electrode material to produce a productthat is chemically stable against the active metal electrode materialand has the desirable ionic conductivity (i.e., a first layer material).Such a reactive material is sometimes referred to as a “precursor”material. The second material layer of the composite is substantiallyimpervious, ionically conductive and chemically compatible with thefirst material. Additional layers are possible to achieve these aims, orotherwise enhance electrode stability or performance. All layers of thecomposite have high ionic conductivity, at least 10⁻⁷ S/cm, generally atleast 10⁻⁶ S/cm, for example at least 10⁻⁵ S/cm to 10⁻⁴ S/cm, and ashigh as 10⁻³ S/cm or higher so that the overall ionic conductivity ofthe multi-layer protective structure is at least 10⁻⁷ S/cm and as highas 10⁻³ S/cm or higher.

A fourth suitable protective membrane architecture is illustrated inFIG. 2D. This architecture is a composite 230 composed of an interlayer232 between the solid electrolyte 234 and the active metal anode 201whereby the interlayer is impregnated with anolyte. Thus, thearchitecture includes an active metal ion conducting separator layerwith a non-aqueous anolyte (i.e., electrolyte about the anode), theseparator layer being chemically compatible with the active metal and incontact with the anode; and a solid electrolyte layer that issubstantially impervious (pinhole- and crack-free) ionically conductivelayer chemically compatible with the separator layer and aqueousenvironments and in contact with the separator layer. The solidelectrolyte layer of this architecture (FIG. 2D) generally shares theproperties of the second material layer for the composite solid statearchitectures (FIGS. 2B and C). Accordingly, the solid electrolyte layerof all three of these architectures will be referred to below as asecond material layer or second layer.

A wide variety of materials may be used in fabricating protectivecomposites in accordance with the present invention, consistent with theprinciples described above. For example, in the solid state embodimentsof Figs. B and C, the first layer (material component), in contact withthe active metal, may be composed, in whole or in part, of active metalnitrides, active metal phosphides, active metal halides active metalsulfides, active metal phosphorous sulfides, or active metal phosphorusoxynitride-based glass. Specific examples include Li₃N, Li₃P, LiI, LiBr,LiCl, LiF, Li₂S—P₂S₅, Li₂S—P₂S₅—LiI and LiPON. Active metal electrodematerials (e.g., lithium) may be applied to these materials, or they maybe formed in situ by contacting precursors such as metal nitrides, metalphosphides, metal halides, red phosphorus, iodine, nitrogen orphosphorus containing organics and polymers, and the like with lithium.A particularly suitable precursor material is Cu₃N. The in situformation of the first layer may result from an incomplete conversion ofthe precursors to their lithiated analog. Nevertheless, such incompleteconversions meet the requirements of a first layer material for aprotective composite in accordance with the present invention and aretherefore within the scope of the invention.

For the anolyte interlayer composite protective architecture embodiment(FIG. 2D), the protective membrane architecture has an active metal ionconducting separator layer chemically compatible with the active metalof the anode and in contact with the anode, the separator layercomprising a non-aqueous anolyte, and a substantially impervious,ionically conductive layer (“second” layer) in contact with theseparator layer, and chemically compatible with the separator layer andwith the exterior of the anode compartment. The separator layer can becomposed of a semi-permeable membrane impregnated with an organicanolyte. For example, the semi-permeable membrane may be a micro-porouspolymer, such as are available from Celgard, Inc. The organic anolytemay be in the liquid or gel phase. For example, the anolyte may includea solvent selected from the group consisting of organic carbonates,ethers, lactones, sulfones, etc, and combinations thereof, such as EC,PC, DEC, DMC, EMC, 1,2-DME or higher glymes, THF, 2MeTHF, sulfolane, andcombinations thereof. 1,3-dioxolane may also be used as an anolytesolvent, particularly but not necessarily when used to enhance thesafety of a cell incorporating the structure. When the anolyte is in thegel phase, gelling agents such as polyvinylidine fluoride (PVdF)compounds, hexafluoropropylene-vinylidene fluoride copolymers(PVdf-HFP), polyacrylonitrile compounds, cross-linked polyethercompounds, polyalkylene oxide compounds, polyethylene oxide compounds,and combinations and the like may be added to gel the solvents. Suitableanolytes will also, of course, also include active metal salts, such as,in the case of lithium, for example, LiPF₆, LiBF₄, LiAsF₆, LiSO₃CF₃ orLiN(SO₂C₂F₅)₂. In the case of sodium suitable anolytes will includeactive metal salts such as NaClO₄, NaPF_(c), NaAsF₆ NaBF₄, NaSO₃CF₃,NaN(CF₃SO₂)₂ or NaN(SO₂C₂F₅)₂, One example of a suitable separator layeris 1 M LiPF₆ dissolved in propylene carbonate and impregnated in aCelgard microporous polymer membrane.

The second layer (material component) of the protective composite may becomposed of a material that is substantially impervious, ionicallyconductive and chemically compatible with the first material orprecursor, including glassy or amorphous metal ion conductors, such as aphosphorus-based glass, oxide-based glass, phosphorus-oxynitride-basedglass, sulpher-based glass, oxide/sulfide based glass, selenide basedglass, gallium based glass, germanium-based glass, Nasiglass, ceramicactive metal ion conductors, such as lithium beta-alumina, sodiumbeta-alumina, Li superionic conductor (LISICON), Na superionic conductor(NASICON), and the like; or glass-ceramic active metal ion conductors.Specific examples include LiPON, Li₃PO₄.Li₂S.SiS₂, Li₂S.GeS₂.Ga₂S₃,Li₂O.11Al₂O₃, Na₂O.11Al₂O₃, (Na,L)_(1−x)Ti_(2−x)Al_(x)(PO₄)₃ (0.1≦x≦0.9)and crystallographically related structures, Li_(1+x)Hf_(2−x)(PO₄)₃(0.1≦x≦0.9), Na₃Zr₂Si₂PO₁₂, Li₃Zr₂Si₂PO₁₂, Na₅ZrP₃O₁₂, Na₅TiP₃O₁₂,Na₃Fe₂P₃O₁₂, Na₄NbP₃O₁₂, Na-Silicates, Li_(0.3)La_(0.5)TiO₃, Na₅MSi₄O₁₂(M: rare earth such as Nd, Gd, Dy) Li₅ZrP₃O₁₂, Li₅TiP₃O₁₂, Li₃Fe₂P₃O₁₂and Li₄NbP₃O₁₂, and combinations thereof, optionally sintered or melted.Suitable ceramic ion active metal ion conductors are described, forexample, in U.S. Pat. No. 4,985,317 to Adachi et al., incorporated byreference herein in its entirety and for all purposes.

A particularly suitable glass-ceramic material for the second layer ofthe protective composite is a lithium ion conductive glass-ceramichaving the following composition:

Composition mol % P₂O₅ 26-55% SiO₂ 0-15% GeO₂ + TiO₂ 25-50% in whichGeO₂ 0-50% TiO₂ 0-50% ZrO₂ 0-10% M₂O₃ 0 < 10% Al₂O₃ 0-15% Ga₂O₃ 0-15%Li₂O 3-25%

and containing a predominant crystalline phase composed ofLi_(1+x)(M,Al,Ga)_(x)(Ge_(1−y)Ti_(y))_(2−x)(PO₄)₃ where X≦0.8 and0≦Y≦1.0, and where M is an element selected from the group consisting ofNd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb and/or andLi_(1+x+y)Q_(x)Ti_(2−x)(Si_(y)P_(3−y)O₁₂ where 0<X≦0.4 and 0<Y≦0.6, andwhere Q is Al or Ga. The glass-ceramics are obtained by melting rawmaterials to a melt, casting the melt to a glass and subjecting theglass to a heat treatment. Such materials are available from OHARACorporation, Japan and are further described in U.S. Pat. Nos.5,702,995, 6,030,909, 6,315,881 and 6,485,622, incorporated herein byreference.

The composite should have an inherently high ionic conductivity. Ingeneral, the ionic conductivity of the composite is at least 10⁻⁷ S/cm,generally at least about 10⁻⁶ to 10⁻⁵ S/cm, and may be as high as 10⁻⁴to 10⁻³ S/cm or higher. The thickness of the first precursor materiallayer should be enough to prevent contact between the second materiallayer and adjacent materials or layers, in particular, the active metalof the anode. For example, the first material layer for the solid statemembranes can have a thickness of about 0.1 to 5 microns; 0.2 to 1micron; or about 0.25 micron. Suitable thickness for the anolyteinterlayer of the fourth embodiment range from 5 microns to 50 microns,for example a typical thickness of Celgard is 25 microns.

The thickness of the second material layer is preferably about 0.1 to1000 microns, or, where the ionic conductivity of the second materiallayer is about 10⁻⁷ S/cm, about 0.25 to 1 micron, or, where the ionicconductivity of the second material layer is between about 10⁻⁴ about10⁻³ S/cm, about 10 to 1000 microns, preferably between 1 and 500microns, and more preferably between 10 and 100 microns, for exampleabout 20 microns.

(iii) Anode Backplane

The anode backplane 106 in physical continuity with the second surfaceof the active metal anode 100 is substantially impervious and providesstructural support for the active metal anode 100 and serves as part ofthe hermetic enclosure. The anode backplane encapsulates the secondsurface of the anode and in various embodiments the backplane is inmechanical force continuity with the anode's second surface. In certainembodiments the anode backplane may be in direct physical contact withthe active metal anode. Depending on its configuration, the anodebackplane may have one or more components and provide additionalfunctions as well. For example, and as described further below, theanode backplane may be or include a current collector and/or electricalterminal connector, or another protective anode architecture resultingin a double-sided protected anode architecture. The anode backplane canalso serve as either the bottom base or top cover of a battery cellcontainer. The anode backplane may also include a compressible materialto moderate anode thickness variations that may arise during dischargeand charge.

Generally, the anode backplane comprises a suitable material orcombination of materials that result in an anode backplane that issubstantially impervious to the external environment surrounding theanode compartment and chemically compatible with internal components.The choice of anode backplane is not limited to a class of materials, inthe sense that the anode backplane may comprise metals, polymers,ceramics and glasses. The anode backplane may be flexible or rigid. Thebackplane should comprise materials with barrier properties and be thickenough to be substantially impervious to its surrounding environment,yet not so thick that it causes undue burden on the overall weight andvolume of the protected anode.

In one aspect of the present invention, the anode backplane 106 includesa laminar composite material comprising multiple layers that providespecific functionality in terms of chemical resistance and barrierproperties against the ingression of ambient moisture and electrolytesolvents including aqueous electrolytes. In one aspect of the presentinvention this anode backplane support component (e.g., 107 of FIG. 1B)is a multi-layer laminate composite comprising a plurality of layers;for example, a laminar composite comprising two or more layers.

A particularly suitable anode backplane support component 107 of thepresent invention comprises a multi-layer laminate composite havingthree or more adjacently stacked layers: a top and a bottom layer and atleast one middle layer. In one aspect of the invention, the bottom layeris adjacent to the second surface of the active metal anode 100; in thisaspect the bottom layer should be chemically compatible with the secondsurface of the active metal anode. In the case of a protected anodecomprising an protective membrane architecture with a liquid anolyteinterlayer, the bottom layer should also be compatible with the anolyte.By compatible with the anolyte, it is meant that the bottom layer doesnot dissolve or swell with the anolyte to the extent that it hinders theintended service life of the protected anode architecture. In apreferred embodiment the bottom layer comprises a low meltingtemperature thermoplastic that is heat-sealable. A particularly suitablebottom layer is low density polyethylene (LDPE). By contrast, the toplayer of this anode backplane component comprising a multi-layerlaminate is chemically resistant to the external environment. The toplayer is also preferably an electronic insulator. A particularlysuitable top layer is polyethylene terephthalate (PET). While all layersof a multi-layer laminate may provide some barrier functionality, atleast one of the middle layers is a barrier layer. A particularlysuitable middle barrier layer is a metal foil with appropriate thicknessto block out ambient moisture and other deleterious penetrants externalto the anode compartment, and also prevents components inside the anodecompartment from escaping. A particularly suitable inner layer isaluminum foil, for example about 30 microns thick. The multi-layerlaminate may include additional middle layers such as metals, polymers,glasses and ceramics. Moreover, the layers may comprise adhesives forbonding the layers together and wetting layers to improve bonding.

The anode backplane component 107 may be molded or embossed to apreformed shape having any number of possible configurations. Forexample it may be molded to include steps that provide a platform to setbonds for the joining of the anode backplane to the compliant sealstructure 104. Other preformed shapes may also be appropriate for easeof manufacture, and to facilitate configuration of anode arrays havingvarious configurations such as cylindrical shapes and spiral wounds.

A particularly suitable anode backplane component 107 comprises aflexible multi-layer laminate manufactured by Lawson Mardon Flexible,Inc. in Shelbyville, Ky., with the product specification Laminate 95014.This laminate is about 120 microns thick, comprising a top layer ofpolyethylene terephthalate (about 12 micron thick); a middle layer ofaluminum foil (about 32 micron thick); a middle layer of polyethyleneterephthalate (about 12 micron thick), and a bottom layer of low densitypolyethylene.

The anode backplane 106 can also be configured to provide currentcollection and a terminal connection. To serve as a current collector,the anode backplane 106 should comprise a suitably conductive andchemically stable material such as a metal (e.g., copper, stainlesssteel, and nickel) that does not alloy with or intercalate the activemetal of the anode. In this embodiment of the invention the anodebackplane serves as current collector and terminal connector. When theactive metal anode 100 is lithium, a particularly suitable, currentcollecting, anode backplane 106 is copper, nickel or stainless steel.Accordingly, the anode backplane may be a suitably thick copper, nickelor stainless steel foil or plate or an expandable copper metal mesh suchas Exmet. As understood by those of skill in the art, it is desired thatthe thickness and weight of the current collector be minimized inbalance and consideration with the need to provide adequate electronicconductance. In one embodiment, the anode backplane comprises abackplane support component 107 and a current collector 108 placedbetween the second surface of the active metal anode 100 and thebackplane support component 107. In this embodiment a particularlysuitable backplane support material is a multi-layer laminate asdescribed above, for example the laminate manufactured by Lawson MardonFlesible; and a suitable current collector is copper foil in the rangeof 8 to 25 microns, e.g., 25 microns, or nickel foil, about 50 micronsthick. In other embodiments, the thickness of the copper or nickelcurrent collector is minimized to be in the range of 5 microns to 15microns.

If the anode backplane is a metal, it may be a suitably thick metal foilor plate that is chosen for its stability against reaction with theexternal environment and coated on the side adjacent to the anode with adifferent metal or conductive material such as copper or a carbon inkthat is particularly stable to the active metal anode. By suitablythick, the anode backplane should provide sufficient structural supportfor the protected anode based on its intended use and be substantiallyimpervious. However, it should not be so thick as to place an undueweight burden on the protected anode. A suitable current collectorbackplane is stainless steel foil in the range of about 25 to about 250microns, e.g., 100 microns.

In another embodiment of the invention, an electronically conductivematerial is coated onto the surface of an non-conductive anode backplanecomponent (such as component 107, described above) to provide currentcollection and/or a terminal connection. In this aspect, the anodebackplane may be any material; preferably, the surface that is exposedto the external environment, outside the anode compartment, isinsulating. The insulator may be any suitable material such as a glass,ceramic or a polymer. Polymers are particularly useful as they are bothlightweight and can have excellent chemical resistance properties. Theelectronically conducting film may be any suitable metal film so long asthe surface in contact with the second surface of the active metal anodeis chemically stable or forms a chemically stable interface. In oneembodiment the electronically conducting film comprises at least onemetal, such as copper (or molybdenum or tantalum), deposited by physicalvapor deposition onto a polymeric substrate, such as PET, to a thicknessof about 2 to 5 microns. In one embodiment, the anode backplane alongwith its electronically conducting surface film extends beyond the anodecompartment such that the electronically conducting film provides aterminal connection from the active metal anode to outside of the anodecompartment. Similarly, the substrate for the current collector/terminalconnection film may be the backplane support component such as amulti-layer polymer/metal laminate composite such as described above.

Moreover, in some instances, the anode backplane, or a componentthereof, may be a single contiguous piece of material forming both thebackplane/component and the compliant seal structure of the protectiveanode architecture. This embodiment of the invention is described inmore detail with reference to FIGS. 3G and 3H, below.

While incorporation of a current collector in the anode backplane 106 isoften preferred, there are instances whereby current collection/terminalconnection is provided otherwise. For example, in certain designs, aterminal connector separate from the anode backplane directly contactsthe active metal anode material. One instance of this is in double-sidedprotected anode architectures in accordance with the present invention,such as described with reference to FIG. 4A, below, wherein the anodebackplane is a second ionically conductive protective membrane andcurrent collection and terminal connection are provided by a separatestructure(s) in electrical contact with the anode. Such an arrangementis also possible in single-sided embodiments such as depicted in FIGS.1A-E.

In order to supply power to an external device, the active metal anodemust be in electronic continuity with at least one electronicallyconductive terminal that extends outside the anode compartment. Incertain embodiments of the invention the electronically conductiveterminal is in direct physical contact with the active metal anode. Inother embodiments, particularly in embodiments that comprise an array ofprotected anodes, an active metal anode may not be in direct physicalcontact with a terminal connector; however, every active metal anode isin electronic continuity with at least one terminal connector.

In the embodiment depicted in FIG. 1B, the anode backplane 106 comprisesa substrate component 107, such as a polymer (e.g., PET) or amulti-layer polymer/metal laminate such as described herein and aterminal connector 110 in electronic continuity with the currentcollector 108. In the illustrated embodiment, a particularly suitableterminal connector 110 is a metal tab. Suitable metal tabs are nickel,aluminum, aluminum alloys, and stainless steel alloys. While the tab mayhave any appropriate geometric form, it should have a low enoughresistance such that it is able to pass the electronic current drawnfrom the anode without excessive heating and or causing significantvoltage drop to the associated battery cell. The tab may be of anylength provided that it is able to extend outside the anode compartment.Nickel is a particularly suitable current collector and a particularlysuitable terminal connector. The current collector and terminalcollector may be resistance welded to each other. In an alternativeembodiment, the current collector and terminal are a single piece ofnickel.

Alternatively, the terminal connector is in contact with the activemetal material of the anode, or simultaneously in contact with both theactive metal material and the current collector. If the terminal 110 isattached to or contacts the active metal material, the terminal 110 mustnot adversely react with the active metal material.

The terminal may be attached to the current collector or the activemetal material of the anode by any of a number of well-known methodssuch as but not limited to soldering, physical pressure, ultrasonicwelding, and resistance welding.

The terminal connector 110 may exit the anode compartment through any ofa number of possible portals such as through the compliant sealstructure 104, or through the anode backplane 106, or preferably asillustrated in FIG. 1B a portal is formed at the junction between thecompliant seal structure 104 and the anode backplane 106.

(iv) Compliant Seal Structure

Referring again to FIG. 1B, the compliant seal structure 104 providesthe surrounding enclosure for the active metal anode 100 and is joinedby sealing to the protective membrane architecture 102 and the anodebackplane 106, which serve to encapsulate the first and second surfaceof the active metal anode, respectively. The compliant seal structure ischemically resistant, substantially impervious and flexible. In variousembodiments, the compliant seal structure is interfaced with theprotective membrane structure and anode backplane to form the anodecompartment; this encompasses instances where the compliant sealstructure is bonded or joined to one or more of the other elements or isotherwise contiguous or made contiguous with one or more of the otherelements, such as when the compliant seal structure and the anodebackplane, or component thereof, are formed from a single piece ofmaterial. For illustration purposes, several embodiments of compliantseal structures showing how they are interfaced with the protectivemembrane architectures and anode backplanes in accordance with thepresent invention are illustrated below in FIGS. 3A-H.

It is a feature of the present invention that as the active metal anode100 volume shrinks or expands, manifested by changes in the active metalthickness, the compliant seal structure 104 deforms in such a manner asto alter the thickness of the anode compartment 130. The deformation isenabled by the compliant seal structure's ability to bend, stretch,compress or generally adapt its shape under an applied load, such as anet force applied against the protective membrane architecture 102and/or the anode backplane 106. Accordingly, if there is a normalcomponent to the net force, or the net force is in the normal direction,the flexibility of the compliant seal structure allows the protectivemembrane architecture to follow the first surface of the active metalanode and/or the anode backplane to follow the second surface of theactive metal anode, in response to mass transfer (leading to anodethickness changes) during charge and discharge.

The extent of the range of motion depends, in part, on the flexuralcharacteristics of the compliant seal structure and the magnitude of thenet force applied to the protected anode architecture. The net force onthe anode compartment is the sum of the external forces applied fromoutside the anode compartment and the internal forces applied by thecomponents of the anode compartment, which includes the active metalanode, the anode backplane, the protective membrane architecture and thecompliant seal structure.

External forces are those that derive from components or environmentsthat are outside and not part of the anode compartment For example,external forces may be generated by battery components such as springs;come about as a result of the environment that surrounds the protectedanode, such as hydrostatic pressure in the case of a metal/seawaterbattery; be induced by electrochemical reactions that drive the cathodeto expand against the protective membrane architecture, such as theformation of discharge products in the case of a metal/air battery Theexternal forces may derive from other phenomena and combinationsthereof.

During discharge, the internal forces (within the anode compartment) aregenerally, but not always, reciprocal forces or reactive forces in thatthey respond to the application of an external force. The internalforces are applied by the components of the anode compartment: activemetal anode, anode backplane, protective membrane architecture and thecompliant seal structure. For example, at rest the net force on theanode compartment 130 is zero, as the external forces applied onto theprotective membrane architecture 102 and anode backplane 106 areabsorbed, in part, by the active metal anode 100. During operation(charge or discharge), as mass is moved into and out of the anodecompartment 130 the thickness of the active metal anode changes, theforces become unbalanced and the protective membrane architecture 102and/or the anode backplane 106 responds by moving with the first andsecond surface of the active metal anode 100, respectively. A compliantseal structure 104 in accordance with the present invention providesenough flexibility and ease of flexure so that a protective membranearchitecture under the influence of the external forces is able totranslate across its entire range of motion while retaining substantialimperviousness. The compliant seal structure 104 may also be undertension, so that it provides a tensile stress rather than a responsiveforce on the ion membrane architecture and anode backplane, tending topull the two in the direction of the active metal anode (e.g., with anextended elastomer relaxing to its non-stretched state).

In various embodiments, in accordance with the protected anodearchitectures of the instant invention, the protective membranearchitecture and/or the anode backplane is provided a significant rangeof motion to move/translate with the first and second surface of theanode, as the active metal anode thickness changes as a result ofelectrochemical oxidation or reduction. In various embodiments, theprotective membrane architecture and/or the anode backplane is able tofollow the first and second surface of the anode, respectively, untilthe anode is fully exhausted. In various embodiments, the protectivemembrane architecture is able to move along with the first surface ofthe anode, and the anode backplane is able to move along with the secondsurface of the anode over distances that generally correspond to thethickness of the anode. In various embodiments, one or both of the anodebackplane and protective membrane are able translate along with theirrespective anode surfaces over distances that are typically greater than10 microns, more preferably greater than 50 microns, even more preferredgreater than 100 microns. In certain embodiments, when the protectedanode architecture is electrochemically oxidized (e.g., during dischargeof a battery) the translation distance afforded one or both the anodebackplane or protective membrane architecture is typically greater than250 microns, preferably greater than 500 microns, and more preferablygreater than 1 centimeter.

The degree to which the anode compartment thickness will shrink orexpand depends on the change in active metal thickness during charge anddischarge and the flexural characteristics of the compliant sealstructure in response to the magnitude and direction of the externallyapplied forces. In an embodiment where the protected anode architectureis used in a primary battery cell, the compliant seal structure shouldallow the thickness of the anode compartment, as measured from the anodebackplane to the ion membrane architecture, to shrink, by as much as thethickness of the anode employed. Similarly, for a secondary batterycell, the thickness of the anode compartment should reversibly shrinkand expand by at least the thickness change that the anode undergoes percycle. In one aspect of the invention, the protected anode structures ofthe present invention may provide a significant range of motion for thethickness of the anode compartment to shrink and expand during dischargeand charge. By a significant range of motion it is meant that thecompliant seal structure provides a range of motion for the thickness ofthe anode compartment (as illustrated in FIGS. 1B and C) to change by atleast 10 microns, more preferably at least 50 microns, even morepreferred is greater than 100 microns. In some aspects of the presentinvention, the range of motion is greater than 250 microns, greater than500 microns, and greater than 1 centimeter.

In various embodiments, both the protective membrane architecture andanode backplane are afforded a significant range of motion so that bothare able to translate as a result of anode thickness changes caused bydischarge or charge. In certain embodiments, only one of the anodebackplane and protective membrane architecture is provided a range ofmotion to translate along with the anode surface that it encapsulates.For instance, in certain embodiments, one or the other of the anodebackplane or protective membrane is joined to a positionally fixed rigidmember, such as a battery container, or casing, or the like, and istherefore precluded from translating as the anode thickness changes.

In one embodiment of the present invention, the compliant seal structureis compliant such that it easily deforms and folds onto itself yetprovides suitable barrier properties. More generally, however, in thedesign of the compliant seal structure there is a compromise between theease of flexure, ruggedness, barrier properties, and ability towithstand continued flex cycles without failure; along with aconsideration of the externally applied forces (magnitude anddirection).

The compliant seal structures of the present invention enable bothprimary and secondary battery cells.

The compliant seal structure may derive its flexibility, barrierproperties and chemical resistance from a combination of intrinsicmaterial properties (e.g., elastic modulus, hardness, ductility,solubility and reactivity); geometric form (e.g., aspect ratio andthickness); and configuration (e.g., folds, crinkles, etc). Within thespirit of the invention the seal structure can derive its properties byany combination of the proper choice of materials (such as polymers,metals, ceramics and glass), geometries (such as films and foils withvarying aspect ratios) and configurations (such as crinkles andaccordion type folds).

In one embodiment of the invention the compliant seal structurecomprises a single material composition having all the requiredcharacteristics of chemical resistance, flexibility, and substantialimperviousness, such as a flexible film, e.g., a flexible metal foil or,depending on service life, a thermoplastic (or otherwise polymeric) filmof sufficient thickness to provide a suitable barrier.

Polymers exhibit a wide range of properties. Some polymers, such aselastomers, are springy, having low elastic moduli typically in therange of 0.01 to 0.1 GPa; and can be reversibly stretched to very largestrain. Most polymers have a slightly higher elastic modulus between 0.1and 5 GPa, so their elasticity varies according to composition andstructure. Even those with relatively high elastic moduli can have alarge plastic deformation range that imparts flexibility. A number ofpolymers, in addition to being flexible, exhibit excellent chemicalresistance and very good barrier properties. Polymers with very goodbarrier properties to moisture include ethylene-vinyl alcohol (EVOH),Polyvinylidene chloride), (PVDC), high density polyethylene (HDPE),polypropylene (PP), polyvinyl chloride) (PVC), polytetrafluoroethylene(PTFE), PVdF and Parlyene C. Others include Butyls, halogenatedisobutylene, co-polymers of isobutylene and paramethylstyrene and theirhalogenated versions.

Unfortunately, no polymers are completely impermeable. The ability of agiven polymer or combination of polymers to provide adequate barrierprotection to make the compliant seal structure substantially imperviousdepends on the intended lifetime of the device, the rate of permeationthrough the barrier, the composition of the permeant, and the wallthickness of the barrier. There is a tradeoff between wall thickness(for improved barrier properties) and flexibility. Polymers are a classof material that, because of their ability to undergo large deformationstrain without breaking, enable relatively thick walled compliant sealstructures having improved ruggedness and adequate barrier properties.Accordingly, in some embodiments of the invention the compliant sealstructure comprises a polymer or combination of polymers having all therequired characteristics of chemical compatibility, flexibility, andsubstantial imperviousness.

The proper balance between flexural characteristics, barrier propertiesand chemical resistance may be achieved by combining more than onepolymer material. For example, a laminar polymer composite, comprising aplurality of polymer layers, effectively combines the properties of eachlayer to provide a more optimal compliant seal structure. For example,the polymer composite may comprise a top chemically resistant layercombined with an inner moisture barrier layer and another inner gaseousbarrier layer followed by a chemically resistant bottom layer andpossibly another heat-sealable layer for bonding the compliant sealstructure to its associated elements (e.g., anode backplane andprotective membrane architecture). For example the polymer composite maycomprise a PTFE outer layer, which has excellent chemical resistanceproperties, with an inner PVDC layer, having excellent moisture andgaseous barrier properties, another inner layer such as EVOH withexcellent gaseous barrier properties, and a polyethylene (HDPE or LDPE)bottom layer with very good chemical resistance properties. Accordingly,in other embodiments of the present invention the compliant sealstructure comprises a combination of polymer materials together to forma laminar polymer composite with improved characteristics andproperties.

While polymers offer significant advantages in terms of chemicalresistance and flexibility, metal foils have excellent barrierproperties. Moreover, ductile metals such as aluminum, alloys ofaluminum and stainless steels, while possessing only moderate elasticdeformation range, are extremely flexible when provided in a geometricform having a high aspect ratio such as in foil format. Depending onmetal foil composition, microstructure and thickness, the problem ofcracks and pinholes formed during device fabrication or operation mayreduce barrier properties. The ruggedness of metal foils may be enhancedby the addition of polymer buffer films or foils that add structuralsupport and ductility. Moreover, a polymer layer on the surface of themetal foil may improve its chemical resistance, while providingelectronic insulation to the compliant seal structure. This is wellknown to those skilled in the art of packaging material for foods,electronic components, and other products that need to be sealed againstan external environment.

Compared with single material layers, the properties of a multilayerlaminate structure can be tailored by varying the composition andthickness of each layer. For example, polymers have excellent mechanicaland chemical properties, but are not impermeable; and while metal foilsare in themselves excellent barrier materials, and are flexible whenthin, they can benefit from a having at least another layer to close offpinholes and insulate surfaces. Accordingly, in some preferredembodiments of this invention the compliant seal structures of thepresent invention are composed of a plurality of layers stacked togetherin a laminar format to provide a substantially impervious, chemicallyresistant and flexible structure.

Accordingly, in various embodiments the compliant seal structure is acomposite made up of a plurality of layers, e.g., a multilayer laminate.The multilayer laminate compliant seal structures of the presentinvention have at least two layers: a top layer adjacent to the externalenvironment about the anode compartment and a bottom layer adjacent tothe internal environment inside the anode compartment. In certainembodiments, the multilayer has at least one or more additional layers(i.e., inner layers) that are interposed between the top and bottomlayers. Without limitation, the inner layer(s) may provide a barrieragainst ingress of air and/or moisture and/or electrolyte into the anodecompartment and/or a barrier against the egress of anolyte (i.e.,electrolyte in contact with the active anode layer) from seeping out ofthe anode compartment; or such inner layer(s) may be incorporated tooptimize or otherwise improve adherence between adjacently stackedlayers; and in certain embodiments one or more inner layers isincorporated (or integrated) in the layer for use as a secondary sealantto cover, and thereby protect, exposed edges of the laminate. That innerlayer, typically a thermoplastic or melt flow polymer, is sometimesreferred to herein as an integrated secondary sealant layer, that,during heat sealing of a compliant seal structure to a protectivemembrane architecture and/or during heat sealing of two compliant sealstructure components, extrudes out and flows over the edge of thelaminate thereby covering and protecting the laminate edges that wouldotherwise, if not for it being covered by the secondary sealant layer,be exposed to the external environment.

In one variant, the multi-layer laminate has at least three layers: i) asubstantially impervious inner barrier layer, ii) a top layer chemicallyand mechanically resistant to constituents of the external environment,and iii) a bottom layer chemically compatible with internalconstituents. The thickness of the individual layers is determined bythe tradeoff between barrier properties, flexibility (thicker filmsprovide improved barrier properties but may impair flexibility) andweight, and in certain embodiments by the need to form a sufficient heatseal. All three layers may have additional desirable properties thatcontribute to the overall ability of the laminate to provide asubstantially impervious and flexible compliant seal structure.Moreover, the laminate may have additional inner layers that, amongother things, improve barrier properties and ruggedness and/or enhanceadhesion of adjacent layers and/or function as an integrated secondarysealant layer as described above and in more detail below.

The individual layers making up the multilayer may be compositionallyand/or micro-structurally homogenous or heterogeneous. For instance, alayer may be a homogenous polymer or a polymeric blend or containmaterial additives (e.g., ceramic particles) to enhance barrierproperties or a non-uniform composition or microstructure in the planeof the laminate may be used to impart variations in the positionalflexibility of the seal structure or to improve barrier properties orchemical resistance.

In one embodiment of the invention the compliant seal structure is alaminate composite comprising a top polymer (or thermoplastic) layerthat is electronically insulating and chemically resistant to theenvironment external to the anode compartment and preferably alsoprovides some mechanical abrasion resistance (e.g., PVDC, PTFE, PET, PPand PE); a bottom polymer (or thermoplastic) layer that is alsoelectronically insulating and chemically resistant to the elementsinside the anode compartment, and is also heat sealable to theprotective membrane architecture (e.g., to its solid electrolyte layer)and anode backplane (e.g., PE, PP, PTFE, PVdF, ethylene copolymers(e.g., ethylene acrylic acid) and ionomer resins such as thosecomprising acid neutralized ethylene acid copolymers such as that whichis referred to by the trademark name Surlyn); and an inner metal foilbarrier layer, (e.g., an aluminum foil of thickness, typically, in therange of 10 to 500 microns), interposed or otherwise sandwiched betweenthe top and bottom layers and which functions to provide an excellentbarrier against the ingress of moisture and gases as well as the egressof elements from within the anode compartment. Additional materiallayers (inner layers) may be incorporated between the metal foil innerlayer and the top and bottom polymer layers. These additional layers maybe polymer layers incorporated to enhance laminate properties includingbarrier properties (e.g., EVOH or HDPE layers), or such layers can beused for adhesive purposes (e.g., as a thin tie or primer layer) toimprove interface strength and bond adhesion between the variousfunctional layers.

In some embodiments of the invention, a sealant may be integrated intothe structure of a multilayer laminate compliant seal structure. Forexample, at least one of the top or bottom outer layers may comprise aprimary sealant layer for bonding, via heat sealing, the multilayerlaminate to the protective membrane architecture and to the anodebackplane, and also for bonding together multilayer laminate compliantseal structure components. Typically the bottom layer serves as theprimary integrated sealant layer. Suitable layers include ionomers,polyethylene, polypropylene, EAA or EMAA, and melt processablefluorpolymers (e.g., PVdF and FEP). Heat sealable thermoplastics softenat relatively low temperatures and may be bonded to a referencecomponent by thermal compression.

In one embodiment of the invention, the heat sealable layer is thebottom layer of a multi-layer laminate compliant seal structure incontact with the internal environment of the anode. Accordingly, thelayer should be chemically resistant and heat-sealable. In order toprevent leaking of anolyte in the case of anolyte interlayer protectivemembrane architectures, such as described above (e.g., with reference toFIG. 2D), the inner thermoplastic layer should be one that does notswell with or dissolve into anolyte. Examples of heat sealable polymerswith resistance to chemical attack by liquid and gel anolytes arepolyethylene, polypropylene, polystyrene, polyphenylene oxide,copolymers of acrylic acid modified polyethylene (EAA) and acrylic acidmodified polypropylene. Other sealant layers include organoclaycomposites, including nanocomposites, where the organoclay may be ablend of an organic compound (e.g., a thermoplastic or other polymer)and a clay, e.g., natural clay.

Improved Ceramic-Polymer Bonding

In embodiments the compliant seal structure is a multilayer laminatehaving a bottom heat sealable thermoplastic layer that serves as aprimary sealant for bonding, by thermal compression, the multilayerlaminate to the solid electrolyte layer, which is typically a ceramic orglass ceramic active metal ion conductor, or inorganic glass. Due to thedissimilarity of these two materials, the bonded interface between theceramic and thermoplastic can be a source of mechanical stressconcentration, and the hydrophilic nature of inorganic surfaces,especially ceramic surfaces, which, generally hydroxylated, have a basicoxide surface that can weaken a ceramic-polymer bond. Accordingly, invarious embodiments the bottom sealant layer may contain acidic groups(e.g., carboxyl groups) or it may be an acidic polymer the acid groupson which provide bonding sites to the basic oxide surface of theceramic. Particularly suitable acidic polymers include copolymers ofethylene (E) and acrylic acid (AA) or methacrylic acid (MAA), forexample ethylene acrylic acid (EAA) or ethylene methacrylic acid (EMAA),and optionally free carboxylate groups on the polymer chains may bepartially or fully neutralized with ions of, for example lithium,calcium or zinc, and preferably lithium in the case where the anode islithium. Another promising copolymer, in this regard, is ethylene-vinylacetate (EVA), although here the polyethylene chain has vinyl acetategroups to enhance adhesion of the bonded interface.

Particularly suitable EAA copolymer for use as a bottom sealant layerfor providing a strong bond to the solid electrolyte layer has, forexample, about 50 to 98 wt. %, preferably about 65 to 95 wt. % ofethylene, and, for example, about 5 to 20 wt. %, for example about 10wt. % of acrylic acid (AA) or methacrylic acid (MA). The copolymer mayhave a number average molecular weight of, for example, about 2,000 to50,000, preferably about 4,000 to 10,000.

As described above, the acid groups provide bonding sites to the basicoxides on the ceramic surface. And by this expedient, increasing theacid level, generally improves adhesion to the ceramic. However, theethylene acid copolymers may not provide the same level of chemicalresistance to external environments that is provided by, for example, anon-polar low-density polyethylene bottom heat sealable layer, and forthis reason when using an acid copolymer as a primary sealant the sealstructure may benefit from the use of a secondary sealant to covers theedges of the laminate.

In some embodiments, extra metal layers (e.g., a second, third or moremetal layers) may be incorporated as inner layers in order to enhancebarrier resistance, in part based on the fact that it is unlikely thatpinholes in one metal foil layer would lineup with pinholes in a secondor third metal foil layer. Multiple inner metal foil layers may havesimilar or different compositions and thicknesses. The use of multiplethin inner metal foil layers (e.g., each layer having a thickness lessthan about 20 microns), as opposed to a single, but relatively thick,metal barrier layer (e.g., thicker than about 20 microns), canpotentially enhance laminate flexibility while providing sufficientbarrier properties.

Metal Layers

Examples of metal foils suitable for use as an inner layer include butare not limited to aluminum, tin, iron, molybdenum, copper, gold,titanium, nickel and stainless steels and their metal alloys includingHastelloy, as well as foils of brazing alloys (e.g., the Cu—In—Tisystem). It is also understood that the flexural properties and strengthof the metal foil barrier layer may be adjusted by adding additionalelements such as by alloying the metal and by heat-treating (i.e.,annealing or tempering) the foil in order to tailor its ductility. Ifthe layer is made too thick, heat sealing can become an issue. Moreover,in forming the laminate a pretreatment may be applied to the metalsurface to create an oxide layer that has better adhesion to the polymerlayer. From the perspective of weight, flexibility and cost, aluminumand aluminum alloys of various tempers and compositions, and especiallythose having a soft temper, are particularly attractive. Particularlysuitable aluminum alloying metals include Si, Fe, Ni, Cu, Mn, Li, Mg,Zn, Cr and Ti, especially aluminum alloys of Si and/or Fe, or Ni.

Besides aluminum, other metals and metal alloys may provide improvedruggedness over the course of bending and stretching such as softtempered copper and its alloys, or metals such as tin and tin alloys(like tin cadmium alloys) which are particularly beneficial from theperspective of reducing adverse chemical reactions; for instance, wheretin and its alloys have enhanced corrosion resistance in contact withseawater. The use of a corrosion resistant metal layer can provide aneeded measure of protection in case moisture and perhaps some saltseventually reach the metal surface and particularly at the metal/polymerlayer interface where enhanced corrosion of the metal can occur. By oneexpedient, the use of a corrosion resistant metal alloy as the barrierlayer or for that matter using a corrosion resistant overlay coatingthat encapsulates the bulk of the metal foil barrier layer can functionto mitigate metal corrosion.

The metal layer or layers may be compositionally and/ormicro-structurally homogenous, or it may have a heterogeneouscomposition and/or microstructure including a surface composition thatis different from that of the bulk, or for that matter having a firstmajor surface bearing one composition and a second major surface bearinga different composition, with either surface composition the same ordifferent than the composition in the bulk of the metal layer. Forexample, suitable overlay coatings may be deposited onto the bulk metalto form one or the other of the metal layer surfaces, or such overlaycoatings may fully encapsulate the bulk metal layer. The composition ofthe overlay coating includes but is not limited to that of a corrosionresistant metal or alloy as well as thin layers of inorganic coatingssuch as silica, titanium nitride and the like.

The metal foil layer, which generally imparts at least some barrierproperties to the laminate in order to prevent the ingress of gas ormoisture, may also be utilized to impart shape-keeping properties to thelaminate in that metal foils can be dead folded as opposed to manypolymers which tend to pull back when bent. The thickness of the metallayer and the number of metal layers and their respective thicknessesmay be adjusted to improve ruggedness and to mitigate cracking which candevelop at corners, particularly when the compliant seal structure ismade into a pre-formed shape (or configuration) by molding the laminate(e.g., by stamping such as by deep or shallow drawing).

The thickness of the metal barrier layer is selected by taking intoaccount the balance between its overall weight, ease of flexure(generally thinner is more flexible) and barrier properties (generallythe thicker the foil the fewer pinholes) as well as the ability to deadfold the laminate when forming a preformed compliant seal configuration.In making a dead fold it is generally the metal foil layer that allowsthe laminate as a whole to keep a configured shape once preformed by,for example, deep drawing the laminate, whereas the polymer layers oneither side of the metal foil, in an elastic response, generally tend topull back on the laminate. The choice of thickness of the metal barrierlayer is a compromise between these competing factors. The metal barrierlayer thickness may be in the range of several microns to hundreds ofmicrons (e.g., 500 microns), preferably the metal foil is about or lessthan 150 microns, and more preferably from about 25 um to about 75 um.

While metal foils such as aluminum are generally excellent barrierlayers, other types of inner layers including thin ceramic layers, thinglass layers and physical vapor deposited materials, such as metals, mayall be used in combination to optimize the balance between barrierproperties, flexibility and chemical resistance. When provided with ahigh enough aspect ratio, thin glasses and thin ceramics offer very goodchemical resistance and barrier properties as well. For example thinfilms of silicon oxide (e.g., SiO₂) can be deposited by PVD or CVD toprovide a moisture and oxygen barrier. The thin layers may be fabricatedby a number of techniques including sputter deposition, CVD, laserablation, e-beam evaporation, etc. Accordingly, in embodiments of theinvention, the compliant seal structure comprises an assemblage of thinlayers of materials such as glasses, polymers, ceramics, metals andcombinations thereof.

Top Layer

In various embodiments of the invention, the compliant seal structure isa multi-layer laminate, the top layer of which contacts the environmentexternal to the anode compartment. The top layer, typically athermoplastic, should have excellent resistance to the externalenvironment, such as strong base as may be encountered in aqueous Li/airbatteries, or organic solvents in non-aqueous batteries (e.g.,non-aqueous lithium air batteries) and constituents of seawater as wouldbe encountered in a Li/Seawater battery cell. Polypropylene, polyisobutylene, PTFE are particularly suitable for use in strong base; PE,PP, PTFE, poly isobutylene have exceptional resistance to organicsolvents, and PE, PP, PTFE, poly isobutylene provide resistance toaqueous environments including seawater. Materials suitable for use as,or as part of, the top layer material of a multilayer laminate for acompliant seal structure include but are not limited to thermoplasticpolymers and copolymers of olefins (e.g., polypropylenes (PP) andpolyethylenes (PE)); diolefins such as butadiene (e.g., polybutadiene),isoprene (e.g., polyisoprene) and the like; vinyl compounds (e.g.,polyvinyl chlorides (PVC), polyvinylidene chlorides (PVdC),polyvinylidene fluorides (PVdF)); acrylonitrile; polyamides; polyesterssuch as polyethylene terephthalate (PET) amorphous PET (APET) andPET-glycol (PETG) and the like; fluoro-polymers; polybutylene (e.g.,polyiosbutylene); polyoxymethylene (POM); polyurethanes; andcombinations thereof including polymer blends as well as compositelayers comprising a polymer from the above list and a second materialsuch as a ceramic additive or overlay coating.

Particularly suitable olefins (also called alkenes) useful as, or aspart of, the top layer include polyethylene (e.g., ultra-high molecularweight polyethylene (UHMWPE), high molecular weight polyethylene(HMWPE), high density cross-linked polyethylene (HDXLPE), cross-linkedpolyethylene (XLPE), high density polyethylene (HDPE), medium densitypolyethylene (MDPE), linear low density polyethylene (LLDPE), or forthat matter low density polyethylene (LDPE) and very low densitypolyethylene (VLDPE) and polyethylene blends thereof; polypropylenesincluding high density polypropylene (HDPE), low density polypropylene(LDPE), and polypropylenes with various stereochemistries including thatof isostatic, syndiotactic, atactic and combinations thereof such asthose made using metallocene catalysis and rubbery polypropylene (e.g.,those having alternating rigid (isostatic) and elastic (atactic)segments), bi-axially oriented polypropylene (BOPP), monoaxial orientedpolypropylene, and polypropylene combinations thereof; polybutylene(e.g., polyiosbutylene); as well as copolymers of ethylene with vinylacetate (EVA) and ethylene with vinyl alcohol (EVOH), and pentane,hexane and the like, and combinations thereof and polymer blends withother olefins or a different type of polymer, as well as compositelayers comprising an olefin polymer from the above list and a secondmaterial such as a ceramic additive or overlay coating.

Particularly suitable top layer vinyl compounds useful as, or as partof, the top layer include polymers and copolymers of vinyl chloride,vinylidene chloride (e.g., PVdC applied as a water-based coating to BOPPor PET in order to reduce permeability to oxygen), vinylidene fluoride(e.g., PVdF can be readily melted by RF and dielectric heating, and itcan be coextruded and laminated; often blends of polymers compatiblewith PVdF are used to achieve bonding), vinylacetate and vinyl alcohol.

Particularly suitable fluoro-polymers useful as, or as part of, the toplayer include polytetrafluoroethylene (PTFE), and melt process fluoropolymers which can be thermoformed to any shape and laminated to avariety of substrates such as fluorinated ethylene propylene (FEP), acopolymer of hexafluoropropylene and tetrafluoroethylne andperfluoroalkoxy (PFA) polymer; polychlorotrifluoroethylene (PCTFE),which has excellent moisture barrier and electrical insulationproperties and is used among other things for packaging corrosionsensitive military electronics; copolymers of ethylene andchlorotrifluoroethylene (ECTFE); and copolymers of tetrafluoroethylene,hexafluoropropylene and vinylidene fluoride (THV).

The thickness of the top (external exposed) layer is a balance betweenruggedness of the structure, barrier properties and flexibility. The toplayer serves, in part, to strengthen and chemically protect the otherlayers of the laminate, particularly to protect the metal foil barrierlayer where such a metal foil layer is incorporated. In variousembodiments the thickness of the polymeric outer layer is, for example,between 5 and 250 microns, or between 10 and 150 microns, or between 10and 75 microns. The thickness of the outer layer is tailored, in part,on the type of material layer, the flexibility of the laminate as awhole based on the ability of the laminate to impart the desired rangeof motion for the anode compartment thickness to follow the thicknesschange of the active layer, and the particular application for which theanode use is intended, such as whether the anode is used in a secondaryor primary battery as well as the intended operational temperaturespectrum of the battery. In the case of a PET top layer material, itsthickness is typically between 5 and 100 microns, preferably between 10and 50 microns. Other materials may have very different thicknessrequirements, such as thin glasses and ceramics that will usually beabout 10 microns or less.

For multilayer laminate compliant seal structures having an integratedprimary bottom sealant layer (typically a heat sealable polyethylenepolymer or copolymer), polypropylene, especially oriented polypropylene(OPP), is a particularly suitable top layer material because it has thecombined advantages of chemical resistance to most anticipated externalenvironments, a low glass transition temperature for improved lowtemperature operation and a high melting point temperature relative tothe most commonly used heat sealable thermoplastics (i.e., polyethyleneand the like).

Bottom Layer

The bottom (internal exposed) layer material, should be chemicallyresistant to adverse attack by elements inside the anode compartment.Common elements include liquid and gel type anolytes such as thosedescribed in the discussion of anolyte interlayer protective membranearchitectures (e.g., with reference to FIG. 2D). Because of theirpotential for both flexibility and chemical resistance, polymers (e.g.,thermoplastics) are particularly suitable as, or to form part of, thebottom layer. Polymers that are particularly stable to common anolytesolvents and salts include polyolefins (especially PE and PP),fluoropolymers (especially PTFE, THV, FEP and PFA), and others like polyisobutylene.

The bottom layer may also be sealed to the protective anode architecture(i.e., the protective membrane and anode backplane) via thermalcompression, RF sealing, using microwaves, or any other suitable methodthat causes the bottom layer to heat, and generally melt, and bond.Particularly suitable materials for heat sealing are polymers. Andparticularly suitable polymers for use as, or as part of, a heatsealable bottom layer include, but are not limited to, polyolefins,fluoropolymers (e.g., particularly THV, FEP and PFA), copolymers ofethylene and acrylic acid (EAA) or ethylene and methyl acrylic acid(EMAA), ionomers (e.g., Surlyn and others) and vinyl compounds(particularly those based on polyvinylidene fluoride and itscopolymers), and combinations thereof including polymer blends andpolymer composites of a polymer and an additive material to improveadhesion or otherwise improve properties.

A particularly suitable olefin polymer for use as, or as part of, a heatsealable bottom layer is polyethylene. And particularly suitablepolyethylene polymers include ultra-high molecular weight polyethylene(UHMWPE), high molecular weight polyethylene (HMWPE), high densitycross-linked polyethylene (HDXLPE), cross-linked polyethylene (XLPE),high density polyethylene (HDPE), medium density polyethylene (MDPE),linear low density polyethylene (LLDPE), or for that matter low densitypolyethylene (LDPE) and very low density polyethylene (VLDPE) andpolyethylene blends thereof. Also suitable are polypropylenes includinghigh density polypropylene (HDPE), low density polypropylene (LDPE).

The bottom layer may also be a composite; for example, a mixture of apolymer or polymer blend and an additive, such as a moisture adsorbentand/or getter of chemical species dispersed in the bottom layer for thepurposes of attracting and retaining chemical species that if present inthe anode compartment might adversely react in contact with the activeanode layer; to prevent such contact, the bottom layer functions as agetter of said chemical species.

The thickness of the bottom layer is a balance between providingruggedness to the structure, barrier properties and flexibility. Andwhen the bottom layer provides a heat seal, its thickness should beadequate for bonding, and for this a balance between having enoughthickness to provide an adequate seal and not so thick as to require aninordinate amount of heat which could damage other material layers orthe component onto which it is heat sealed. Generally, the bottom layerthickness is between 25 and 400 microns, preferably between 50 and 200microns.

In various embodiments when the bottom layer is an integrated primarysealant it is bonded to a component of the architecture via thermalcompression.

In certain embodiments the integrated bottom sealant layer may RFsensitive and therefore heat sealed inductively, for example by using RFsealing techniques. In one embodiment, the integrated bottom sealantlayer is particularly sensitive to RF heating, such as PVdF.

It is to be understood that the glass transition temperature (Tg) of thevarious polymer layers (thermoplastic layers) may be adjusted, e.g.,lowered, by modifying the material layers such as by co-polymerizationand blending of polymers, adjusting the polymer molecular weight and/ormolecular weight distribution, cross-linking, incorporating variouspendant groups which can be used, for instance, to alter free volume inthe polymer, and by adding plasticizers which can be used in certaininstances to dramatically lower the glass transition of the polymerlayer.

In one particular illustrative embodiment the low temperature compliantseal is a multilayer laminate having a metal foil barrier layer (e.g.,an aluminum or aluminum alloy), a polyolefin top protective layer and apolyolefin bottom sealant layer. For example the top polyolefin layer isa polypropylene layer (e.g., biaxially oriented polypropylene BOPP orrubbery polypropylene) and the bottom sealant layer is a polyethylene(e.g., LDPE, LLDPE, or MDPE or a blend thereof). Or in anotherembodiment, the top and bottom layer are both polyethylene layers, thebottom layer as described above and the top layer made from a higherdensity polyethylene material layer. To facilitate ease of heat-sealing,the top layer preferably has a melting temperature above that of thebottom sealant layer. In another example the outer layer may be apolymer that is plasticized in order to enhance its flexibility andparticularly its flexibility at low temperature, such as plasticized PVC(e.g., PVC plasticized with phthalates) or plasticized PET orplasticized polyolefins (e.g., PE plasticized with polybutene).

Secondary Sealant Layer in a Multilayer Laminate Compliant SealStructure

Depending on the configuration of the compliant seal structure and themanner in which it is attached (or bonded) to the protective membranearchitecture and/or anode backplane, the multilayer laminate may haveexposed edges. With reference to FIG. 24A, there is depicted,schematically, a multilayer laminate compliant seal structure heat sealbonded, by thermal compression, to a solid electrolyte layer, andtherein the figure also illustrates an exposed edge. Dependent upon thecomposition of the various material layers and the anticipated servicelife of the anode, that exposure, at the edge, can be problematic.

As illustrated in FIG. 24A, various layers of the laminate, many ofwhich may not be optimized for chemical resistance, may, as a result ofthe exposed edge, be susceptible to adverse reactions with the externalenvironment. For instance, a metal foil barrier layer may corrode in thepresence of seawater. Or a heat sealable bottom layer in contact withstrong base may lose adhesion to the solid electrolyte layer. Forinstance, ethylene acid co-polymers (e.g., EAA) are a class of acidicpolymers which are particularly suitable for providing a strong bond toa ceramic or glass ceramic solid electrolyte layer; however, the acidcontent of the polymer, as described above, is a compromise between bondstrength and chemical resistance; the more acid groups, the better theadhesion. But in the presence of a basic electrolyte solution (e.g.,that which may be encountered in a Li/Air battery cell), the acid groupson the polymer chain might otherwise prove detrimental to the long-termstability of the seal.

As described above, edge exposure can lead to delaminating of the layersand may compromise bond adhesion, and, as a result, lead to a subsequenthermetic breach of the anode compartment concomitant with premature cellfailure.

With reference to FIG. 24B, exposed edges of the laminate may beprotected with a discrete secondary sealant, typically applied after theprimary seal has already been made. Suitable discrete secondary sealantsinclude, but are not limited to, epoxy sealants or thermoplastic polymerstrips or coated resins which may be heat sealed or otherwise meltformed over the exposed edges. The discrete sealant provides aprotective cover for at least the bottom sealant layer and preferablythe inner barrier layer, when present. Typically it provides protectionover the entire edge. Other types of discrete sealants includechemically resistant overlay coatings of a glass, ceramic or polymer ormetal deposited over the exposed edges using a masking depositiontechnique. For instance, by physical vapor deposition of a chemicallyresistant glass or ceramic, or electro-less plating of a corrosionresistant metal (e.g., tin or its alloys are especially suitable as adiscrete sealant for a seawater battery cell). For overlay coatings amask will generally be used to ensure that the coat is deposited overthe exposed edge and to minimize the potential for unduly coating theactive surface of the solid electrolyte layer.

Alternatively, or in addition to a discrete sealant, an integratedsecondary sealant layer, incorporated as an inner layer of a multilayerlaminate compliant seal structure, may be used to cover, and therebyprotect, material layers at the laminate edge from unwanted exposure tothe environment of which it opposes.

For instance, with reference to FIGS. 24C-D, a laminate having athermoplastic inner layer with suitable melt-flow properties may be usedfor this purpose, where during thermal compression bonding of thelaminate to the solid electrolyte layer, the secondary sealant layerextrudes, via melt/flow, out of the laminate to form a coating over theedge and on a nearby portion of the solid electrolyte layer surface.This coating is sometimes referred to herein as an extrusion coating. Bythis expedient the bottom sealant layer of the laminate is protected, bythe extruded coating, against contact with constituents of the externalenvironment. Preferably, the extruded coating also provides sufficientprotection for the metal foil barrier layer(s) and, for that matter, allinner layers interposed between it and the bottom layer.

Thermoplastic materials suitable for use as a secondary integratedsealant layer in a multilayer laminate compliant seal structure includethose which are described above for their use as a bottom sealant layer,and in particular polymers therein having sufficient chemical stabilityin contact with the anticipated external environment. Because theadhesion between the bottom laminate layer and the solid electrolytelayer provides the primary bond that holds the seal structure to theprotective membrane architecture, the secondary sealant (integrated ordiscrete) may be primarily chosen for its melt/flow properties andchemical resistance. To achieve thorough coverage of the exposed edge,as characterized above, the thickness and composition of the secondaryand primary integrated sealant layers are tailored accordingly, as arethe thermal compression parameters during heat sealing.

Method of Making Laminate

In various embodiments, the compliant seal structure is a multilayerlaminate having a protective top layer, a bottom sealant layer, and aninterior barrier layer interposed between the top and bottom layers,where generally both the top protective layer and the bottom sealantlayer are polymeric and the barrier layer is a metal foil layer.Additional material layers may be incorporated between the top layer andthe barrier layer and/or between the bottom layer and the barrier layer,and these additional layers may be incorporated to provide furtherbarrier properties (e.g., a second or third or more metal foil layer) orsuch additional layers may be used for adhesive purposes (e.g., as anintermediary tie layer between layers) or more generally to provide anoverall benefit to the compliant seal.

The multilayer laminate for use as a compliant seal structure may bemade by any process suitable for making a multi-layer laminate, such asextrusion/co-extrusion coating, extrusion/co-extrusion lamination,multilayer blown film plant and film lamination including therein wet(solvent) and dry (solventless) film lamination. Extrusion coating is aprocess that lays a molten layer of polymer onto a substrate layer, andgenerally the molten layer is viscous but will flow and wet thesubstrate surface evenly. Extrusion lamination is the combination of twolayers using a molten polymer layer. The molten polymer layer is at thecenter of the sandwich, which enters the nip of the extruder laminator.Film lamination, on the other hand, is the combination of two layersadhered to each other using a laminating adhesive. The adhesive isgenerally coated onto one substrate and generally dried in an oven if itcontains solvent, and then combined with the other layer in a heated nipstation using pressure. In many instances a primer is used to enhancebonding of the layers. In some instances a laminating adhesive can beused as a primer such as polyurethane or polyester. Some materials suchas polyethylene imine or ethylene acrylic acid polymers are formulatedspecifically for use as a primer.

In forming the laminate the metal foil barrier layer functions to act asa barrier to oxidizing agents and it is common that the metal layer isdeposited or extruded onto the surface of a polymer layer, which therebybecomes a carrier as well as a further barrier layer. Suitable polymercompounds as a metal-adherent for bonding between the metal layer andpolymer layers of the laminate include ethylene acrylic and ethylenemethacrylic acid copolymers, ionomers (e.g., polyethylene-methacrylicacid ionomers) and polyethylene or other appropriate polyethylene orpolypropylene derivatives.

Forming the Laminate into a Pre-Form

In various embodiments the compliant seal structure is made into aperformed shape prior to fabricating the protected anode architecture bymolding it using for example a pressing operation such as a deep orshallow draw process (also sometimes referred to as stamping orembossing) or other method of shaping and forming to a desiredconfiguration.

In various embodiments, the multilayer laminate compliant seal structureis constructed into a pre-form by molding (i.e., forming) componentparts using a pressing operation (e.g., deep or shallow draw) thattransforms the shape of the laminate with material retention. Properchoice of material layers, including composition and thickness, and themanner in which the individual layers are pre-treated (e.g., annealingof a metal foil layer to optimize its temper) are key to optimizing thelaminate for deep draw processing. In various embodiments, the depth towhich a pre-form is stamped depends on the thickness of the anode.Generally, in order for the compliant seal structure to fit the anodeinside the anode compartment, the thicker the anode—the deeper the draw.And the mechanical burden on the laminate increases with draw depth,where in the course of stamping some of the material layers, e.g., thepolymeric and/or metal layers under plastic deformation may formpinholes or stress cracks which will adversely affect the barrierproperties of the laminate and may render the compliant seal structureunsuitable for its intended use to provide a hermetic seal. Properchoice of material layers is important to shape pressing (i.e., molding)the laminate without damaging its barrier properties. In particular, theproper choice of metal barrier layer should be made, when such a metalbarrier layer is incorporated in the laminate, and this includes notonly the composition of the metal layer and its associated temper, whichmay be adjusted by heat treating and alloying, but the composition ofthe metal layer in combination with its thickness should be considered.Generally, the thicker the metal layer the stiffer; however, thickermetal layers have more volume so they can stretch more during thedrawing process without pinholing or tearing and therefore may allow, insome instances, for a deeper draw than a thinner layer of the samematerial. Moreover, it should be understood that while the originalthickness of the metal layer, prior to drawing, may be too thick in thatit imparts rigidity to the laminate which makes it unsuitable for itsintended use as a compliant seal structure, deep drawing the laminatewill thin out the metal layer and by this expedient the drawn (pressed)laminate will have sufficient flexibility to make a suitable a compliantseal. Other parameters to consider when molding the laminate include thetooling such as the type of die and its surface finish and operatingparameters such as punching speed, force and temperature.

Accordingly, in one embodiment of the invention the compliant sealstructure comprises a laminate composite comprising a first polymerlayer that is electronically insulating and chemically resistive to theenvironment external to the anode compartment (e.g., EVOH, PVDC, PTFE,PET, Surlyn), a second polymer layer that is also electronicallyinsulating and chemically resistive to the elements inside the anodecompartment (e.g., PE, PP, PTFE, ionomer resins such as those comprisingacid neutralized ethylene acid copolymers commonly referred to by thetrademark name Surlyn), and a third metal foil layer (e.g., Al foilthickness range 10-150 microns) sandwiched between the first and secondlayers that provides an excellent barrier to the ingression of moistureand gases as well as the egress of elements from within the anodecompartment. Compared to single material layers, the properties of amulti-layer laminate structure can be tailored by varying thecomposition and thickness of each layer. For example, polymers haveexcellent mechanical and chemical properties, but are not impermeable;and while metal foils are in themselves excellent barrier materials, andare flexible when thin, they can benefit from a having at least anotherlayer to close off pinholes and insulate surfaces. Accordingly, in somepreferred embodiments of this invention the compliant seal structures ofthe present invention are composed of a plurality of layers stackedtogether in a laminar format to provide a substantially impervious,chemically resistive and flexible structure; such as a multi-layerlaminate.

The multi-layer laminate compliant seal structures of the presentinvention have at least two layers: a top layer and a bottom layer.Additional layers between the top and bottom layers may, among otherthings, improve barrier properties and ruggedness. The top and bottomlayers are chemically resistant to the environment they contact. In onevariant, the multi-layer laminate comprises three layers: i) asubstantially impervious inner/middle barrier layer, ii) a chemicallyresistant outer-top layer, and iii) a chemically resistant outer-bottomlayer. The thicknesses of the individual layers are determined by thetradeoff between barrier properties, flexibility (thicker films provideimproved barrier properties but impaired flexibility) and weight. Allthree layers may have additional desirable properties that contribute tothe overall ability of the laminate to provide a substantiallyimpervious and compliant seal structure. In instances whereby the middlelayer is exposed to the external or internal environment of the anodecompartment, it should be chemically stable with those environments orbe sealed off in some manner such as the application of a discretesealant, for example an epoxy sealant. Discrete sealants suitable foruse in accordance with the present invention are described in moredetail below.

Examples of metal foils used for the middle barrier layer include butare not limited to aluminum, tin, copper, and stainless steels. From theperspective of weight and flexibility, aluminum is preferred. However,other metals may provide improved ruggedness over the course of bendingand stretching such as ductile copper alloys. The thickness of the metallayer is selected by taking into account the balance between its overallweight, ease of flexure and barrier properties. The thickness of themetal barrier layer is preferably in the range of several microns to 150microns, more preferably from about 25 um to 75 um.

While metal foils such as aluminum are generally excellent barrierlayers, thin ceramic layers, thin glass layers and physical vapordeposited materials, such as metals, may all be used in combination tooptimize the balance between barrier properties, flexibility andchemical resistance. When provided with a high enough aspect ratio, thinglasses and thin ceramics offer very good chemical resistance andbarrier properties as well. For example thin films of silicon oxide(e.g., SiO₂) can be deposited by PVD or CVD to provide a moisture andoxygen barrier. The thin layers may be fabricated by a number oftechniques including sputter deposition, CVD, laser ablation, e-beamevaporation, etc. Accordingly, in embodiments of the invention, thecompliant seal structure comprises an assemblage of thin layers ofmaterials such as glasses, polymers, ceramics, metals and combinationsthereof.

The materials of the laminate should be chemically resistant to theenvironments with which they are in direct contact. This includes theenvironment external to the anode and the internal environment of theanode. The external environment may include battery electrolytescomprising aqueous or non-aqueous solvents, seawater, and ambient air.The internal environment may include a variety of non-aqueous solventsused in the formulation of anolytes that stable to the active metal.

In embodiments of the invention, the compliant seal structure is amulti-layer laminate, the top layer of which contacts the environmentexternal to the anode compartment and the bottom layer of which contactsthe environment internal to the anode compartment. Materials withexcellent resistance to anticipated external environments such as strongbase as is encountered in Li/air batteries are polypropylene, polyisobutylene, PTFE, Other materials such as PE, PP, PTFE, polyisobutylene have exceptional resistance to organic solvents, and stillothers such as PE, PP, PTFE, poly isobutylene provide resistance toaqueous environments including seawater. The thickness of the top(external exposed) layer (external exposed) is a balance betweenruggedness of the structure, barrier properties and flexibility. In thecase of a PET top layer material, its thickness is typically between 5and 100 microns, preferably between 10 and 50 microns. Other materialsmay have very different thickness requirements, such as thin glasses andceramics that will usually be about 10 microns or less.

The bottom (internal exposed) layer material, should be chemicallyresistive with elements inside the anode compartment. Common elementsinclude liquid and gel type anolytes such as those described in thediscussion of anolyte interlayer protective membrane architectures(e.g., FIG. 2D). Materials that are particularly stable to commonanolyte solvents and salts include PE, PP, PTFE, poly isobutylene.Again, the thickness of the bottom layer is a balance between ruggednessof the structure, its barrier properties and flexibility. In the case ofa polyethylene layer, the bottom layer is between 25 and 400 microns,preferably between 50 and 200 microns. Other materials may have verydifferent thickness requirements, such as thin glasses and ceramics thatwill usually be less than 10 microns.

In some embodiments of the invention, a sealant may be integrated intothe structure of a multi-layer laminate compliant seal structure. Forexample, at least one of the top or bottom outer layers may comprise aprimary sealant layer for bonding the multi-layer laminate to theprotective membrane architecture and to the anode backplane. Forexample, such a layer may be made of ionomer, polyethylene,polypropylene or other polymers known to those skilled in the art ofheat-sealable plastics used in the packaging industry. Thesethermoplastics soften at relatively low temperatures and may be bondedto the protective anode architecture by thermal compression. In oneembodiment of the invention, the heat sealable layer is the bottom layerof a multi-layer laminate compliant seal structure in contact with theinternal environment of the anode. Accordingly, the layer should bechemically resistive and heat-sealable. In order to prevent leaking ofanolyte in the case of anolyte interlayer protective membranearchitectures, such as described above (FIG. 2D), the innerthermoplastic layer should be one that does not swell with or dissolveinto anolyte. Examples of heat sealable polymers with resistance tochemical attack by liquid and gel anolytes are polyethylene,polypropylene, polystyrene, polyphenylene oxide, acrylic acid modifiedpolyethylene and acrylic acid modified polypropylene.

A particularly suitable compliant seal structure 104 of the presentinvention comprises a multi-layer laminate composite having three ormore adjacently stacked layers: a top and a bottom layer and at leastone middle layer. In a preferred embodiment the bottom layer comprises alow melting temperature thermoplastic that is heat-sealable. Aparticularly suitable bottom layer is low density polyethylene (LDPE).By contrast, the top layer of this compliant seal structure comprising amulti-layer laminate is chemically resistant to the externalenvironment. The top layer is also preferably an electronic insulator. Aparticularly suitable top layer is polyethylene terephthalate (PET).While all layers of a multi-layer laminate may provide some barrierfunctionality, at least one of the middle layers is a barrier layer. Aparticularly suitable middle barrier layer is a metal foil withappropriate thickness to block out ambient moisture and otherdeleterious penetrants external to the anode compartment. A particularlysuitable inner layer is aluminum foil, for example about 30 micronsthick. The multi-layer laminate may include additional middle layerssuch as metals, polymers, glasses and ceramics. Moreover, the layers maycomprise adhesives for bonding the layers together and wetting layers toimprove bonding.

Another particularly suitable complaint seal structure comprises or is amultilayer laminate having a top and bottom polyolefin layer, and aninner metal foil barrier layer. For example, the top layer is apolypropylene layer (e.g., biaxially oriented polypropylene) and themetal foil inner layer is an aluminum metal layer of about 25 to 100microns thick (or more than one metal foil layer may be incorporated toimprove barrier properties) and the bottom layer is a polyethylene heatsealable layer (e.g., a LDPE blend with LLDPE). Or in another suchembodiment the bottom layer is or comprises ethylene arcylic acidco-polymer or ethylene methyl acrylic acid copolymer.

The compliant seal structure may be molded or embossed to a preformedshape having any number of possible configurations. For example it maybe molded to include steps that provide platforms to set bonds. Otherpreformed shapes may also be appropriate for ease of manufacture, and tofacilitate configuration of anode arrays having various configurationssuch as cylindrical shapes and spiral wounds.

A particularly suitable compliant seal structure 104 comprises aflexible multi-layer laminate manufactured by Lawson Mardon Flexible,Inc. in Shelbyville, Ky., with the product specification Laminate 95014.This laminate is about 120 microns thick, comprising a top layer ofpolyethylene terephthalate (about 12 micron thick); a middle layer ofaluminum foil (about 32 micron thick); a middle layer of polyethyleneterephthalate (about 12 micron thick), and a bottom layer of low densitypolyethylene.

It should be noted that while the elastic modulus is a good measure of amaterial's degree of reversible flex, in the context of the presentinvention, the flexible structure may achieve its range of motion by anymechanism including irreversible processes, such as plastic deformation.The range of plastic deformation dictates a materials plasticity orductility. While stiffness and ductility are both intrinsic materialproperties that, in part, determine the degree and ease of flexure, animportant criteria to be considered for choosing an appropriatecompliant seal structure in the context of this invention is thecapability of the compliant seal structure to provide the required rangeof motion to the seal over the lifetime of the protected anode.Accordingly, in embodiments of the present invention the compliant sealstructure may comprise metal foils and plastic foils that arepre-stressed, both elastically and plastically, to enhance their degreeand ease of flexibility.

In addition to the proper choice of material and aspect ratio, theconfiguration of the compliant seal structure can impart flexibility aswell as enhance ruggedness to the seal structure. For example, thecompliant seal structure may be molded into a preformed article prior tobonding to the protective membrane architecture and/or the anodebackplane. The article may comprise a variety of configurations such asaccordion folds or a series of steps having varying angles between eachstep. Accordion folds, such as those common for bellows, can impartpliancy due to the flex of their corrugations, and enhance ruggednessthereby improving the ability for the seal structure to withstand thestress and strain of being flexed and bent during processing andoperation Likewise, random wrinkles and crinkles (pre-wrinkling) by wayof plastic deformation can impart added range and ease of motion to amaterial such as a metal foil, thermoplastic or combinations thereof.

As previously described, increasing its aspect ratio can augment theflexibility of the compliant seal structure. This can be done bydecreasing thickness, which is a compromise with barrier properties; orby increasing the length of the structure, including providing angledconfigurations such as, but not limited to, S shapes, Z shapes, invertedZ shapes, C shapes and inverted W shapes. Adding flexibility to thecompliant seal structure by means of its configuration widens the choiceof suitable materials. Moreover, certain structural configurations haveother benefits such as providing a platform for bonding the compliantseal structure to the anode backplane and protective membranearchitecture. Of course there is a practical limit to improving flexuralproperties by geometric manipulation alone, in the sense that the lengthof the compliant seal structure should be balanced with an attempt tominimize the space it occupies and the area it deactivates. Aparticularly useful configuration for the compliant seal structures ofthe present invention may be described as a double step structure havingan oblique, acute or right angle between steps. This shape providesadded flexure and a convenient platform for bonding.

Referring again to FIG. 1B, the compliant seal structure 104 has adouble-step configuration having a first step 142 and second step 144and an oblique angle between steps. Each step provides a bondingplatform, and the distance and angle between steps is a design criterionthat depends, in part, on the thickness of the active metal anode andthe flexural properties of the compliant seal structure. The angle is atradeoff between minimizing wasted space and ease of flexure. The depthof each step determines the maximum width of the bonding platform. Thewidth of the bond is an important criterion, balanced between being aswide as possible, in order to obtain a strong, hermetic bond andminimized as the area becomes electrochemically de-activated by thebond, creating both wasted volume and lost active area.

As illustrated in the embodiment of FIG. 1B, the inner surface of thefirst step 142 of the compliant seal structure 104 is bound to theprotective membrane architecture 102. The inner surface of the secondstep 144 is bonded to the anode backplane 106. The bond can generally beset anywhere on the protective membrane. While FIG. 1B shows the bond tobe set on the surface of the protective membrane architecture 104adjacent to the environment external to the anode compartment, theinvention is not limited to this arrangement.

The inner surface of the second step 144 of the compliant seal structure104 is bonded to the anode backplane 106. Likewise, the compliant sealstructure 104 may be bonded to any portion of the anode backplane,including the surface that is adjacent to the active metal anode or onthe opposing surface, bearing in mind the desire to optimize hermeticityof the seal while maximizing the active metal anode surface arearelative to the total area of the protected anode. Referring back toFIG. 1B the compliant seal structure is bonded to the surface of theanode backplane that is adjacent to the active metal anode.

It should also be noted that the overall geometry of the anode is squarein the embodiment illustrated in FIG. 1A-E (seen particularly in FIG.1D), it could equally well be any shape such as rectangular or circular.The choice of geometry depends on the eventual device application, thematerials properties of the device components, and other performanceoptimization parameters.

Referring now to FIGS. 3A-H, there is illustrated a variety of compliantseal structures in accordance with the present invention with variousconfigurations and bond placements. The drawings are depicted in columnslabeled I, II and III: column I illustrates a three-dimensional (3-D)perspective of an edge of the compliant seal structure; column II showsthe edge in cross-sectional depiction as it appears in the context ofprotected anode architecture drawings; and column III illustratescross-sections of the protected anode architectures having the variouscompliant seal structures.

Eight different configurations are illustrated in FIGS. 3A-H. In alleight depicted embodiments the protected anode architecture comprises anactive metal anode, 300, a compliant seal structure 304 bonded to aprotective membrane architecture 302 and an anode backplane 306(including, in some embodiments forming a portion of the anodebackplane). The main differences among the embodiments are theconfiguration of the compliant seal structure and the location of thebond between the compliant seal structure and the protective membranearchitecture and anode backplane. There is one further difference thatis particular to the embodiments illustrated in FIG. 3G and FIG. 3H inthat in these embodiments the compliant seal structure and the anodebackplane share a contiguous piece of material.

The compliant seal structure 304 illustrated in FIG. 3A is like thatpreviously described with reference to FIG. 1B. It comprises adouble-step configuration having a first and second step and an obliqueangle between steps. Each step provides a platform for bonding. The bondbetween the compliant seal structure 304 and the ion membranearchitecture 302 is located between the inner surface of the first stepand the top surface of the protective membrane architecture 302. Thesecond step is bonded between its inner surface and the bottom surfaceof the anode backplane. The angle between steps may be adjusted tofine-tune the flexural characteristics of the compliant seal structure304. For example, a greater angle (more oblique) between steps providesease of flexure. As the angle decreases, approaching 90 degrees, asillustrated in the compliant seal structure 304 shown in FIG. 3B, thereis a tradeoff between ease of flexure and volume savings with respect tounused space in the anode compartment.

The compliant seal structure 304 in FIG. 3C, has what may be termed astraight configuration; bonded on its edge to the bottom surface of theion membrane architecture 302, preferably directly on the surface of theimpervious ionically conductive layer. The compliant seal structure 304is bonded on its opposing edge to the bottom surface of the anodebackplane 306. While this configuration has a seemingly minimalfootprint, the edge needs to be wide enough to provide enough surfacearea for adequate bonding. Accordingly, for thin compliant sealstructures 304 that do not provide adequate surface area for edgebonding, a discrete sealant 312 can be applied that engulfs the edge andcovers part of the nearby inner and outer surfaces, as illustrated inFIG. 3D. Particularly useful discrete sealants are room or moderate(<200° C.) temperature curing epoxies that are substantially imperviousand chemically resistant, such as Hysol E-120HP, a polyamidemanufactured by Loctite Corporation or poly-isobutylene of averagemolecular weight from 60,000 to 5,000,000, preferably from 700,000 to2,500,000.

In the preceding examples, the angles illustrated for a double-stepconfiguration have ranged from nearly perpendicular to oblique. If theangle between steps of a double step configuration is acute, it is moreappropriately termed a Z or inverted Z configuration. In FIG. 3E, a Zconfiguration is illustrated with the bonds located on the outer andinner surface of the compliant seal structure 304 between the bottomsurface of the protective membrane architecture 302 and the bottomsurface of the anode backplane 306, respectively. Again, it ispreferable that the bond on the ion membrane architecture 302 be locatedon the surface of the impervious ionically conductive layer.

Another configuration for the compliant seal structure 304, that ofaccordion like folds with a bond placed on the top surface of the anodebackplane 306 and the top surface of the protective membranearchitecture 302 is illustrated in FIG. 3F. FIG. 3F also illustrates theembodiment of multi-sealant practice, whereby a discrete secondarysealant 312 covers the seams and area where the primary sealant wasapplied. For example, the edge of a compliant seal structure comprisinga multi-layer laminate might expose its inner metal barrier layer and anintegrated heat-sealable thermoplastic layer used as a primary sealant,to the environment external to the anode compartment. A chemicallyresistive and substantially impervious discrete sealant applied on theedge of the heat seal would provide chemical protection againstcorrosion of the barrier layer and prevent permeants from seepingunderneath or swelling the thermoplastic layer. Again, a particularlysuitable discrete secondary sealant is Hysol E-120HP and anotherparticularly suitable discrete secondary sealant is poly-isobutylene ofaverage molecular weight from 60,000 to 5,000,000, preferably from700,000 to 2,500,000.

In FIG. 3G there is illustrated a compliant seal structure component 304bonded to the ion membrane architecture 302 and to the anode backplane306. In this embodiment, the anode backplane 306 and the compliant sealstructure component 305 share a common, contiguous piece of material. Ina preferred embodiment the compliant seal structure and the anodebackplane both have a thermoplastic heat-sealable inner layer of thesame composition, which leads to particularly strong heat seal bonds andfacilitates the incorporation of a portal for a terminal connector suchas a tab.

Finally in FIG. 3H there is illustrated a compliant seal structure 304that is bonded to the protective membrane architecture and wraps aroundthe backside of the anode 300, such that the anode backplane 306 and thecompliant seal structure 304 again share a common, contiguous piece ofmaterial.

As noted above with reference to the various compliant seal structureembodiments, a sealant (or sometimes more than one) is used to bond thecompliant seal structure to the protective membrane architecture and tothe anode backplane. Generally, any sealant can be used so long as itprovides the necessary strength to maintain the bond over the lifetimeof the device and is substantially impervious and chemically resistantas described above. The proper choice of sealant is important as itshould be matched to the material properties of the anode compartment interms of chemical compatibility and processing conditions such astemperature. Special consideration should be given to matching materialsproperties. As previously described, a number of the preferred compliantseal structures of the present invention comprise polymers that degradeat relatively low temperatures (<350° C.) and as a result requiresealants that bond at low temperature, and preferably room temperature.Moreover, the components inside the anode compartment may be verysensitive to temperature, such as the active metal anode and liquidanolyte. Preferred sealants of the present invention are set below themelting or glass transition temperatures of either or any of thematerials being joined. Particularly useful sealants are low meltingtemperature thermoplastics bound by thermal compression (e.g., LDPE,LDPP, etc), and chemically resistive epoxy sealants that can be set atmoderate or room temperature, such as Hysol E-120HP and others such aspoly isobutylene of average molecular weight from 60,000 to 5,000,000,preferably from 700,000 to 2,500,000.

While adhesive sealants, such as Hysol E-120HP or poly isobutylene(average molecular weight from 60,000 to 5,000,000, preferably from700,000 to 2,500,000) and thermo-plastic sealants such as LDPE and LDPPthat are bound by thermal compression are preferred, they are not theonly type of discrete sealant useful for the instant invention. Forinstance, in the case where the compliant seal structure or materialsbeing joined do not comprise thermally sensitive material, a number ofalternative sealants and sealing techniques may be employed includingglass seals, brazing, solder seals etc. For example, in the instanceswhere the protective membrane architecture comprises a fully solid statearchitecture, and the compliant seal structure comprises thermallystable materials such as metals and ceramics, such alternative sealantsmay be employed.

In some embodiments, the sealant is an integral component of thecompliant seal structure, for example, a low melting temperaturethermoplastic layer forming a surface of a multi-layer laminatestructure. Such a thermoplastic bottom layer softens at relatively lowtemperature and is bonded using thermal compression (heat-sealing). Whena liquid or gel anolyte interlayer protective membrane architecture(FIG. 2D) is used, the heat sealable thermoplastic bottom layer shouldbe chemically stable with and should not be swelled by the liquidanolyte impregnated in the interlayer. Examples of suitable heatsealable layers include ionomer, polyethylene, polypropylene,polystyrene, Surlyn, polyphenylene oxide, acrylic acid modifiedpolyethylene and acrylic acid modified polypropylene. In otherembodiments the integrated sealant is an adhesive such as polyisobutylene that may be coated onto the compliant structure prior tobonding to the protective architecture or anode backplane.

Discrete sealants such as epoxy sealants (e.g., Hysol E-120HP), oradhesive sealants such as poly isobutylene as opposed to sealants thatare an integral component of the compliant seal structure, may also beused as a primary seal, bonding the compliant seal structure to itsopposing surface; such as the surface of the protective membranearchitecture and/or the surface of the anode backplane. Discretesealants may also be used as a secondary sealant; for example, aroundthe seams where a primary sealant was already applied, for examplearound the edges of a heat sealed thermoplastic. Such a multi-sealsystem improves ruggedness of the primary seal and barrier properties.It is within the scope of the invention to use a multi-sealant systemcomprising heat-sealable integrated sealants and discrete sealants ofvarying compositions and combinations thereof. In the instances where aheat-seal bond is a primary bond, the secondary and tertiary sealantsetc. are preferably processed at temperatures below the softeningtemperature of the heat-seal thermo-plastic. Particularly usefulsecondary sealants dispensed on a heat seal seam are epoxy adhesivessuch as Hysol E-120HP. Further useful discrete sealants are polyisobutylenes.

In another embodiment of the invention, a parlyene coating can be usedas a discrete non-primary sealant to enhance barrier properties aroundanode compartment seams. Paralyene has excellent chemical resistance andcan be used to make conformal coatings around edge seals or over theentire compliant seal structure. Paralyene coatings may be particularlyuseful for coating the edges of compliant seal structures that use aprimary heat sealable thermoplastic to bond the protective membranearchitecture. For example, paralyene may be applied around the seamsusing a masking method to avoid coating sensitive areas such as thesurface of the protective membrane architecture. Furthermore, parylenecoatings are conformal so they may be utilized to improve the barrierproperties and insulating character of the compliant seal structure ingeneral; for example, coating the structure to infiltrate and/or coverpinholes.

Pre-treatments of the protective membrane surface can be used to enhancethe strength and stability of the bond between the protective membraneand the compliant seal structure. These include treatments to roughenthe surface of the membrane such as chemical etching (acid or base) andmechanical grinding. A particularly suitable etchant is concentratedlithium hydroxide. Moreover, the membrane surface around its perimetermay be coated with a primer such as thin layers of inorganic compoundschemically stable in catholytes and anolytes. The thickness range forsuch primer coatings are from about 0.01 to 5 um, preferably from 0.05to 0.5 um. Particularly suitable primer coating compounds are metalnitrides such as SnN_(x) and titanium nitride that may be prepared byphysical vapor deposition such as reactive sputtering in a N₂atmosphere. Other suitable primers include oxides such In₂O₃, SnO₂, andTiO₂ that may be prepared by sol-gel method, thermal evaporation,chemical vapor deposition and by pyrolysis.

Referring back to FIG. 1B, in a preferred embodiment the compliant sealstructure 104 comprises an integrated sealant layer, such as a LDPElayer, that bonds by thermal compression the compliant seal structure tothe protective membrane architecture 102 and the anode backplane 106. Inthe embodiment illustrated in FIG. 1B, the anode backplane support 107is also a multi-layer laminate comprising a low melting temperaturethermoplastic inner layer of a similar if not the same composition.

While the embodiment illustrated in FIGS. 1A, D and E suggests that thecompliant seal structure is fabricated in the form of a unified windowframe, within the scope of the invention, the compliant seal structuremay comprise discrete structures and elements or combinations ofdiscrete structures and elements bonded together to effectively form aunified compliant seal structure.

In one preferred embodiment of the present invention both the compliantseal structure and the anode backplane have a thermoplasticheat-sealable inner layer of LLDPE. Having both materials beingheat-sealable and of the same composition leads to particularly strongheat seal bonds and facilitates the incorporation of a portal for aterminal connector such as a tab. As illustrated in FIG. 1B, the tab isjoined to the anode current collector inside the anode compartment, andexits the anode compartment from a portal between the compliant sealstructure 104 and the anode backplane 106. To strengthen the bond andits hermeticity, the terminal connecting tab may be blanketed and/orcoated with a thermoplastic resin having a low melt temperature such asLDPE.

Low Tg Compliant Seal Structures

The operating temperature of the protected anode architecture and theextent to which that temperature may fluctuate or otherwise change overthe course of operation depends, in large measure, on the temperature ofthe external environment about the device in which the anode isincorporated (e.g., ambient air or seawater surrounding a Li/Air orLi/Seawater battery, respectively). Generally, the device will haveassociated with it a specification sheet specifying, among otherparameters, a temperature range over which the device is intended tooperate, including a predefined upper and lower bound operatingtemperature. Those bounds, or temperature limits, may be derived fromthe anticipated environment in which device use is intended, or by someother parameter, such as a low temperature limitation in the batterychemistry.

For instance, in a seawater battery cell of the instant invention thelowest operating temperature the cell may experience will depend ondepth, geographic location, season and time of day. Accordingly, aseawater battery cell of the instant invention will have a predefinedlower bound operating temperature dependent upon its intendedapplication, including, in various embodiments, a lower boundtemperature of about 15° C., or about 10° C., or about 5° C., or about0° C., or even colder than that, e.g., down to about −4° C. (which isabout the lowest temperature that seawater is known to reach). Likewise,the anticipated operating temperature of a metal air battery (e.g., aLi/Air battery) of the instant invention will also depend on itsintended application, and in certain embodiments it will have a lowoperating temperature bound of about: 0° C., −10° C., −20° C., −30° C.;or as low as −40° C.

Accordingly, in certain embodiments, the instant invention is intendedfor operation inclusive of low temperature, which is defined herein tomean a temperature below about 15° C.

While it is generally understood that material properties will change asthe temperature drops, these changes may occur gradually and may onlybecome evident under certain circumstances, including time spent at lowtemperature or the rate of temperature change. Particularly at lowtemperature, where kinetics are hindered, unforeseen complications canarise which may only become apparent after the fact and can takesubstantial time to manifest. In other instances, material changes maytake place sharply, occurring, as the temperature decreases, in realtime, but the change may only take place or become evident at or below aspecific low temperature, where such an abrupt change may have adramatic and perhaps immediate affect, such as when a material undergoesa low temperature induced phase change or state of matter transitionthat weakens its mechanical integrity, or when a material experiences asignificant increase in its elastic modulus, such as that which may takeplace below a material's glass transition temperature (Tg).

According to various embodiments, the low temperature performance of theprotected anode architecture and battery cells of the instant inventionmay be enhanced in a multilayer laminate compliant seal structure byselecting certain material layers having a glass transition temperaturethat is lower than the predefined lower bound operating temperaturelimit of the protected anode architecture or the device in which it isincorporated.

Generally, many thermoplastic materials are characterizable (e.g., bydifferential scanning calorimetery) as having a glass transitiontemperature where above the transition temperature the material layer isin a rubbery state. And by extension, a compliant seal structurecomprising such a thermoplastic material layer is, itself, on the whole,also characterizable as having a thermoplastic glass transitiontemperature corresponding to that of the thermoplastic layer. Whenmultiple thermoplastic material layers are employed, the seal structuremay have several Tg values, and, in turn, is characterizable as havingan uppermost temperature glass transition (or uppermost glass transitiontemperature) corresponding to the thermoplastic material layer havingthe highest Tg.

When used as a component layer in a compliant seal structure, a low Tgmaterial layer has the advantage that above its glass transitiontemperature it remains in a rubbery state, where it is beneficially mostflexible. Below Tg, its elastic modulus may increase, and the layer maystiffen.

Accordingly, in one embodiment of the invention, the compliant sealstructure is a multilayer laminate having an uppermost thermoplasticglass transition temperature that is below the predefined low operatingtemperature limit of the anode architecture, or below the predefinedlower bound operating temperature of the device in which it isincorporated (e.g., battery cell).

The so-called glassy or rubbery state of a material is but one factor toconsider when selecting an appropriate thermoplastic material layer foruse in a multilayer laminate compliant seal. Another parameter, which isto be considered in conjunction with Tg, is the layer's thickness. Forinstance, a relatively thin polymeric or thermoplastic material layer(e.g., an inner tie layer or outer conformal glass coating) may have arelatively high glass transition temperature which is above the lowoperating temperature limit, but will not cause undue stiffening when ata temperature below its Tg because it is so thin. On the other hand, arelatively thick thermoplastic material layer, with a thickness above acertain threshold value, will have a pronounced improvement inflexibility at low temperature if the operating temperature of the anodearchitecture remains, at all times, above the layer's Tg. The thresholdthickness above which a material layer's glass transition becomes animportant factor in the stiffening, at low temperature, of the compliantseal structure is generally in the range of from about 200 microns to aslow as about 5 microns, for example about 100 microns, or about 50microns, or about 20 microns, or about 10 microns.

Accordingly, in certain preferred embodiments of the invention, thecompliant seal structure is a multilayer laminate wherein nothermoplastic material layer of thickness greater than 200 microns, orgreater than 100 microns, or 50 microns or 20 microns or greater than 10microns or greater than 5 microns has a glass transition temperatureabove the lower bound operating temperature of the protected anodearchitecture or that of the device in which it is incorporated.

Yet another parameter to consider when optimizing the seal structure forlow temperature performance and flexibility is the arrangement of thevarious layers, in that the top and bottom layers, which are generallythe thickest, may have the most pronounced effect on the flexibility ofthe laminate, and therefore maintaining them in a rubbery state may be,in certain embodiments, paramount to the seal's flexibility.Accordingly, in certain preferred embodiments the Tg of the top andbottom thermoplastic material layers of a multilayer laminate compliantseal structure is below the lower bound operating temperature of theprotected anode architecture or device thereof. That is, neither layer(top or bottom) has a glass transition temperature greater than thelower bound operating temperature limit.

According to the above provisos, and bearing in mind that the lower theTg the less likely there is to be an abrupt change in the elasticmodulus of the laminate, particularly suitable thermoplastic materiallayers for use in a multilayer compliant seal structure of a protectedanode architecture of the instant invention and battery cell thereof,and which are intended for operation inclusive of low temperature, arepolymer layers (thermoplastic layers) having a glass transitiontemperature that is below room temperature (i.e., below about 15 C), andpreferably below 10 C, below 5 C, below 0 C, or below −5 C, and evenmore preferably below −10 C, below −20 C, below −30 C, and yet even morepreferably below −40 C, depending upon the desired operatingtemperature.

It is to be understood that the glass transition temperature of thevarious polymer layers may be adjusted, e.g., lowered, by modifying thematerial layers such as by co-polymerization and blending of polymers,adjusting the polymer molecular weight and/or molecular weightdistribution, cross linking, incorporating various pendant groups whichcan be used, for instance, to alter free volume in the polymer, and byadding plasticizers which can be used in certain instances todramatically lower the glass transition of the polymer layer.

In one particularly suitable illustrative embodiment the compliant sealstructure is a multilayer laminate having a polyolefin top layer ofpolypropylene and a polyolefin bottom layer of polyethylene and a metalfoil inner layer (e.g., aluminum foil), where both the top and bottompolymer layers have a Tg that is below at least one or all of theoperating/external/ambient temperature of the anode architecture.

In another illustrative embodiment the multilayer laminate has a toppolyolefin layer and a bottom sealant layer, where both top and bottomlayers have a glass transition temperature that is below at least one orall of the operating/external/ambient temperature of the anodearchitecture, and where particularly suitable bottom sealant layersinclude polyolefins including polyethylenes and polypropylenes and EAAand EMAA.

In another particular illustrative embodiment the compliant seal is amultilayer laminate having a metal foil barrier layer (e.g., an aluminumor aluminum alloy), a polyolefin top protective layer and a polyolefinbottom sealant layer. For example the top polyolefin layer is apolypropylene layer (e.g., biaxially oriented polypropylene BOPP orrubbery polypropylene) and the bottom sealant layer is a polyethylene(e.g., LDPE, LLDPE, or MDPE or a blend thereof). Or in anotherembodiment, the top and bottom layer are both polyethylene layers, thebottom layer as described above and the top layer made from a higherdensity polyethylene material layer. To facilitate ease of heat-sealing,the top layer preferably has a melting temperature above that of thebottom sealant layer. In another example the outer layer may be apolymer that is plasticized in order to enhance its flexibility andparticularly its flexibility at low temperature, such as plasticized PVC(e.g., PVC plasticized with phthalates) or plasticized PET orplasticized polyolefins (e.g., PE plasticized with polybutene). Inanother example the multilayer laminate compliant seal structure hasthree layers: a bottom EAA layer; a top OPP layer; and an inner aluminumalloy barrier layer; and optionally an additional secondary integratedsealant layer of LDPE.

Alternate Embodiments

Basic parameters of the invention have been described above withreference to several embodiments. The invention may also be embodied inseveral other anode structure architectures, arrays and cells, examplesof which are described below:

Double-Sided Anode Structure

One alternative embodiment of a protected anode architecture of thepresent invention is illustrated in FIGS. 4A-C. FIG. 4A depicts across-sectional view of the protected anode architecture in a fullycharged state; FIG. 4B depicts a cross-sectional view of the protectedanode architecture in a partially discharged state; and FIG. 4C depictsa perspective view of the protected anode architecture. The protectedanode architecture 420 has a double-sided structure. The structure isdouble sided in the sense that active metal ions are available to leaveand enter the protected anode architecture from both planar surfaces.The protected anode architecture 420 comprises an active metal anode 400having a first and second surface. Adjacent to the first surface of theactive metal anode is an protective membrane architecture 404 andadjacent to the second surface is the anode backplane 406, which in thisembodiment is a second protective membrane architecture. A currentcollector 408, e.g., a nickel foil is embedded inside the activematerial of the active metal anode. In one embodiment, the active metalmaterial is Li and the anode is formed by adhering Li foil to both sidesof the current collector, for example, by pressing. In anotherembodiment, the active metal material of the anode may be coated on bothsides of the current collector with a composite coating comprising anactive metal intercalating material such as graphite.

In the depicted embodiment, each of the two protective membranearchitectures 402 and 406 are bonded to respective compliant sealstructure components 404 and 405. The compliant seal structurecomponents are molded into preformed frames with a first and second stepand having slightly oblique angles between each step. The first step ofthe compliant seal structure 404 is bonded to its respective protectivemembrane architectures 402. In the same fashion, the second protectivemembrane architecture is bonded to the second compliant seal structurecomponent. The second step of each compliant seal structure component isbonded to each other, around the periphery of the anode compartment.Thus, the final structure was built-up from two separate double-stepstructures. Of course, other configurations are possible, as discussedabove.

A particularly suitable compliant seal structure of the presentinvention comprises a multi-layer laminate having a heat sealablethermoplastic bottom layer. Accordingly, these compliant seal structuresare heat-sealed to their respective protective membrane architecturesand to each other.

Referring back to FIG. 4A, the current collector 408 is joined to aterminal connector 410. The terminal connector may be attached to thecurrent collector and/or the active metal material of the anode by anyof a number of well-known methods such as but not limited to soldering,physical pressure, ultrasonic welding, and resistance welding.

The terminal tab 410 extends to the outside of the anode compartment andin one embodiment of the invention it exits the anode compartment at thejunction where the first and second compliant seal structure components404/405 are bonded together. In the instance whereby the compliant sealstructure components are multi-layer laminate materials, the terminaltab can be encapsulated by the bottom layer thermoplastic material ofthe two compliant seal structure components 404/405 by thermalcompression. In order to ensure an hermetic seal is formed around thetab, the terminal tab 410 may be coated with a low melting temperaturethermoplastic or have a low melting temperature thermoplastic filmwrapped around its surface in the area of the heat seal. A suitablethermoplastic is polyethylene or polypropylene.

While in most embodiments the double-sided protected anode architectureis symmetric in that the second layer material of both protectivemembrane architectures (or the solid electrolyte in the case ofmonolithic architectures) are roughly of the same composition andthickness, there are some instances whereby the functionality of thedevice would benefit or be derived from asymmetry. In one aspect theasymmetry may be realized by modifying the chemical composition, atomicstructure and/or thickness of the second material layer such that onemembrane is substantially different from the other. In another aspect,the double-sided protected anode architecture may comprise an activemetal anode bisected by an electronic insulator such that the electricalcurrent through opposing protective membranes (membranes on either sideof a double-sided protected anode architecture) is under independentelectrochemical control.

Protected Anode Arrays

The present invention also encompasses protected anode architecturearrays comprising an assemblage of individual protected anode cells.Having an array of protected anode cells offers design versatility interms of augmenting the dimension of the anode, enabling conformal arraystructures capable of conforming to the surface of varying structuralshapes and providing for arrays having various configurations such ascylindrical and spiral wound designs.

Flexible arrays offer an added degree of ruggedness during handling andmanufacture as well as device deployment and operation. For example, inthe case of an metal/seawater battery that is open to the ocean,protected anode architecture arrays of the present invention which havesome degree of flexure offer significant benefit in terms of ruggednessfor such an underwater application. Moreover, the flexible arrays havean additional benefit of being conformal and this facilitates a numberof advantages with respect to volume optimization of a battery cell thatneeds to fit a certain volume and shape requirement. While theindividual cells are all hermetically sealed from the externalenvironment, in part, by a flexible compliant seal structure, the bodyof the array may be rigid or flexible. The flexural character of thearray is determined by the pliancy of the compliant seal structure andin the case of arrays comprising cells that share a common anodebackplane, by the flexibility of the anode backplane as well.

In some embodiments of the invention the individual cells of the arrayshare a common anode backplane, in other arrangements the array can takeon a number of configurations including planar and cylindrical shapes.The arrays may be rigid or flexible. In other embodiments the array maycomprise double sided anode cells; and in other embodiments of theinvention a particularly pliant array provides enough flexibility forspiral winding.

A single-sided protected anode array 520 is illustrated in FIG. 5A (witha cut-away to reveal the various layers). The array shown in FIG. 5A isdesignated a 4×4 planar array in that the array is four cells acrosseach row and there are four rows. For the sake of convenience in thisdescription of the embodiment, the array dimensions are defined by thenumber of cells along a given row, designated as m cells and by thenumber of rows, designated as n rows. For example, an array with 3 rowsand 6 cells per row is termed in m×n nomenclature as a 6×3 array. Them_×_n arrays of the present invention may take on any configurationincluding planar or cylindrical. It should also be clear that theinvention is not limited to arrays of cells that are distributed in astrictly perpendicular arrangement or for that matter having any orderedarrangement whatsoever. In fact, the arrays may comprise an apparentlyrandom arrangement of anode cells.

The protected anode cells of the array may be of any geometric shape anddimension; though they are generally squares, rectangles or circles. InFIG. 5A the individual protected anode cells are square. Moreover, whileit may be the case that each of the protected anode architectures is ofthe same dimension, the individual protected anode cells of a givenarray can be of different size and shape. In fact, varying shape andsize of the individual protected anode architecture cells providesflexibility for the design of the array configuration and can impartpliancy to the body of the array. Accordingly, in one embodiment, thedimension of each cell varies in its width such that it enables theprotected anode array to be spiral wound. The radius of curvature aroundeach bend depends in part on the progressive variation of the cell widthalong a given direction of the array. This embodiment is describedfurther below with reference to FIG. 7.

Referring back to FIG. 5A, the protected anode array 520 in this examplecomprises 16 cells configured as a 4×4 matrix. The individual cells arestructurally similar to the embodiment illustrated in FIGS. 1A-E, whichis that of a single sided protected anode architecture. Each of the 16cells of the array comprise an active metal anode 500 having a first andsecond surface; and each cell has an protective membrane architecture502 adjacent to the first surface of its active metal anode. In theembodiment shown in FIG. 5A, better viewed in the correspondingalternative cross-sectional views for FIGS. 5B and 5C, the individualcells of the array share a common anode backplane support component 507.The common anode backplane support component is substantially imperviousand adjacent to the second surface of the active metal anode of eachcell. The anode backplane may be rigid or flexible.

In a preferred embodiment the anode backplane support component isflexible. A suitably flexible anode backplane is or includes amultilayer laminate such as a flexible multi-layer laminate manufacturedby Lawson Mardon Flexible, Inc. in Shelbyville, Ky., with the productspecification Laminate 95014. This laminate is about 120 microns thick,comprising a top layer of polyethylene terephthalate (about 12 micronthick); a middle layer of aluminum foil (about 32 micron thick); amiddle layer of polyethylene terephthalate (about 12 micron thick), anda bottom layer of low density polyethylene. Such multi-layer laminatesare particularly attractive as common anode backplanes as they form verystrong heat seal bonds to the compliant seal structures of the samecomposition. Moreover, the multi-layer laminates are relativelylightweight and impart excellent barrier properties to the array.

Referring now to FIG. 5B, the array illustrated is representative ofwhat is termed a closed array design, whereby each individual cell isenclosed within its own anode compartment by a compliant seal structure504 that is bonded to a given cell's protective membrane architecture502 and to the common anode backplane support component 507. Thecompliant seal structure may be provided as 16 individually preformedstructures or as a single compliant seal structure having 16 internalframes in a unified compliant seal structure. In another embodiment,each row of the array comprises its own pre-formed compliant sealstructure. In the instance illustrated in FIGS. 5A and B this wouldamount to a compliant seal structure having four internal frames that isbonded, for example by a heat seal, to the common anode backplanesupport component 507.

The protected anode arrays of the present invention may vary widely withrespect to the configuration of the electronic connection among cellsand the output to the external environment. The distribution ofelectronic connections among cells effectively forms an electronicallyconductive network that comprises electronically conductinginterconnects for cell-to-cell current collection and terminalconnectors for electrical output to the external environment.

In one embodiment, the active metal anode of each individual cell hasits own terminal connector that is in electrical continuity with therespective anode and extends outside the enclosure of the array. Thistype of configuration offers the most control over each individual celland enables the utility of external electronic circuitry tomonitor/control each protected anode cell individually. A tradeoff withthis configuration is the increased likelihood of a seal breach simplydue to the large number of seals that surround each external port.Accordingly in this aspect of the invention it is particularly useful tomake use of a secondary room temperature curing adhesive sealant, asdescribed above, such as Hysol E-120HP, around the seams at the junctionbetween the compliant seal structure and the anode backplane.

In another embodiment, the protected anode architecture array comprisesa common anode backplane that is an electronic conductor such as astainless steel foil or plate and that provides electronic continuityfor the entire array and a terminal connection. In some circumstancesthis aspect of the invention provides advantages as there is no need toprovide additional terminal connections and subsequent seals forelectrical output.

The array designer has the flexibility to choose between the simplicityof a common anode backplane providing both current collection and aterminal connection, and having electronic control of each anode cellindividually, and/or combinations thereof.

A balance between these two designs is embodied in the array illustratedin FIG. 5A, where there is provided a separate terminal connector 510for each row of the array. Hence, there are four terminal connectors andeach one provides output current from the four cells in its given row.To do so, the anode backplane 506 of each cell comprises a currentcollector 508 positioned at the back of the active metal anode and thecurrent collectors are electronically interconnected by a suitablyconductive material, such as a metallic foil tab. Alternatively, thecurrent collector behind the active metal anodes of each row maycomprise a unified structure that extends to each cell along the row andthereby maintains electronic continuity among cells of a given row.

An alternative to a closed array design, shown in FIG. 5C, is an openarray design whereby the protective membrane architecture of each cellis joined together by a compliant seal structure and is only joined tothe anode backplane around the periphery of the array. This effectivelyleaves the anode compartment of adjoining cells open to each otherwithin the array. In order to seal off the array from the environment,the cells at the periphery of the array are bound to an anode backplane.The open array design provides an open inner structure and, perhaps,greater flexibility at the joint between cells. In contrast, the closedarray design, offers significantly more control over the performance ofeach cell as the volume of each anode compartment is able to adjustindependently.

For a given anode cell size, for example determined by the size of theprotective membrane architecture, the anode arrays of the presentinvention provide a way to augment the size of an associatedelectrochemical device such as a battery cell. Referring to FIGS. 5B andC. a battery cathode 518 can be placed adjacent to the protectivemembrane architecture 502 of the 4×4 protected anode array to form abattery cell comprising the array. In one embodiment of the inventionindividual cathodes cover each anode cell of the array and in anotherembodiment a single cathode can be large enough to cover the entiresurface of the array.

The arrays of the present invention may also be flexible in the sensethat the array is able to conform to a variety of structural shapesproviding ruggedness to the overall character of the array. Theconformability of the array depends on the flexural characteristics ofthe compliant seal structure, as well as the array design, such as openor closed, and in some embodiments in which the array comprises a commonanode backplane, the flexibility of the anode backplane becomes adetermining factor to the overall conformability of the array. Forarrays that comprise individual anode cells that do not share a commonbackplane, in other words each has its own distinct anode backplane, theflexure of the array is determined by compliancy of the seal structure.Generally, for arrays that have a common anode backplane, the flexuralcharacter of the array depends on the pliancy of both the compliant sealstructure and the flexibility of the anode backplane, which is afunction of the constitution and configuration of the anode backplane.

The protected anode arrays of the present invention can be configuredinto a wide variety of shapes, including cylindrical and spiral wound.Referring to FIGS. 6A and 6B, the arrays 640 are provided in cylindricalgeometry in which the anode backplane 606 is a cylinder that is commonto all cells in the array. The protected anode array is essentiallycurved around the inner circumference of the cylinder as shown in FIG.6A and around the outer circumference of the cylinder in FIG. 6B. Thearray may be rigid or flexible. In one embodiment of the invention thearray is fabricated in a planar fashion and then rolled into a cylinder.In another embodiment the cells are fashioned onto a rigid cylindricalanode backplane. Referring to FIG. 6A, the individual anode cells 620 ofthe array comprise an active metal anode 600 having a first and secondsurface. The first surface is adjacent the protective membranearchitecture 602, the second surface is adjacent the anode backplane606. The compliant seal structure 604 is joined to the protectivemembrane architecture 602 and to the anode backplane 606, and enclosesthe anode around its perimeter.

In the configuration illustrated in FIGS. 6A and 6B, the array has aclosed design as each cell is individually sealed to a common anodebackplane 606. The anode backplane may comprise a flexible polymerhaving a metal grid coated onto its surface in order to collect currentfrom each active metal anode and to transfer current from each cell to aterminal connector. As noted above, the array may have a terminalconnector for each cell, or it may have a terminal connector for adesignated number of cells, or there may be one terminal connector forall the cells of the array. The flexible polymer backplane may be rolledinto a cylinder format as illustrated in FIGS. 6A and 6B. In anotherembodiment, the cells can share a common anode backplane which may be ametal cylinder such as a copper cylinder. In this aspect the currentcollection and terminal connection are accomplished by the coppercylinder. The protected anode array 640, as it would be employed in abattery, comprises a cathode 618, or an electron transfer structure 618as would be the case if water was employed as the depolarizer. Thecathodes may be located anywhere in the interior of the cylinder for theembodiment illustrated in FIG. 6A; and anywhere on the exterior of thecylinder shown in FIG. 6B. In FIG. 6A individual cathodes are locateddirectly adjacent the protected anodes inside the cylinder. In FIG. 6B asingle cathode is effectively wrapped about the exterior of thecylinder. For example, in a metal/seawater battery, the cells of thearray are exposed to seawater. In one instance the seawater may berushing through the interior of the cylinder or around the exterior ofthe cylinder. While a cylindrical shape is illustrated in theembodiment, the array can be quite conformal and may take other forms.In one embodiment, the array is on a flexible anode backplane, providingsome degree of conformity. In another aspect, the array may take theform or shape of an apparatus such that it may be placed in a conformalmanner adjacent to the apparatus. Furthermore, by adjusting the shapeand size of the individual cells of a given array, the array can be mademore conformal, for example around edges and corners. This isillustrated further in the embodiment illustrated in FIGS. 7A-B

A number of battery performance parameters are dependent on the apparentarea of the anode and cathode. In one array embodiment of the presentinvention, the apparent active area of the array is doubled by adouble-sided assemblage. A double sided anode array 740 is illustratedin FIGS. 7A and B. The array comprises individual protected anodearchitecture cells 720 that are strung together to form a row of cells.Each cell comprises an active metal anode 700 having a first and secondsurface. The first surface of the active metal anode 700 is adjacent theprotective membrane architecture 702 and the second surface is adjacentthe anode backplane 706. As the embodiment is that of a double sidedanode, the anode backplane is a second protective membrane architecture.A compliant seal structure component 704, in the form of a double stepconfiguration, is bonded to the protective membrane architecture 702 anda second compliant seal structure component 705 is bonded to the anodebackplane 706 (second protective membrane architecture). The twocompliant seal structure components are bonded together to compete thecompliant seal structure and enclose the cell. The cells are inelectronic continuity having electronically conductive interconnectsencapsulated between compliant seal structures of the first and secondprotective membrane architecture. The interconnects run across thelength of the array 740 until they reach an end cell whereby a terminalconnector extends to the outside of the array 740.

As shown in FIG. 7B, the physical length of each cell in the directionalong the row of cells progressively changes, starting from the firstcell, which has the longest length, to the last cell, which has thesmallest length. Provided that the compliant seal structure components704, 705 have the appropriate flexural character to allow the structureto bend around the desired radius of curvature, this design allows forthe array to be spiral wound as shown in FIG. 7A. The radius ofcurvature around each bend depends in part on the degree of progressivevariation of the cell dimension along the array length and theflexibility of the compliant seal structure. In FIG. 7B the cells do notshare a common anode backplane so their flexibility depends on thepliancy of the compliant seal structure 704, 705. By winding spiral theapparent surface area of the array 740 is increased within a volumetricstructure having a smaller footprint than a planar array of the samearea.

An alternative array embodiment is illustrated in FIGS. 8A-B. The arraycomprises double sided protected anode architectures as described abovethat are linked together and emanate from a center point, where theterminal connection is made. This arrangement is likened to a hub andspoke arrangement whereby the spokes correspond to an array of cellsconnected together at the hub. Such a hub and spoke arrangement isparticularly useful to augment surface area for a metal/seawater batterycell, and is also particularly useful for redox flow cells. In apreferred embodiment, each array of cells, along the direction of aspoke, shares a common anode backplane that is rigid enough to providestructural support to the array. Ideally the common anode backplanecomprises a strong yet lightweight material, such as a carbon composite.

The catholyte (e.g., seawater, redox active liquids) essentially fillsthe regions between anode arrays (spokes). An appropriate cathodestructure comprising at least one of an electronically conductivematerial, not drawn, could be located adjacent to each of the arrays.There is a limit for the length of each spoke in terms of optimizingbattery cell volume, in the sense that as the spokes get longer thevolume between spokes gets progressively larger. In the configurationillustrated in FIG. 8B, essentially an array of so-called “spoke andhub” arrangements is illustrated. Effectively, this array of arraysmakes for a denser packing of protected anode cells.

Electrochemical Cell Structures

The invention of a protected lithium anode such as are described incommonly assigned co-pending published US Applications US 2004/0197641and US 2005/0175894, and their corresponding International PatentApplications WO 2005/038953 and WO 2005/083829, respectively thedisclosures of which are incorporated by reference herein in theirentirety and for all purposes, offers significant advantages in thedesign of new electrochemical cell structures based on such anodes,including the ability to use active metal electrodes in conjunction withcathode structures and catholytes that if not for the protectivemembrane architecture would corrode the anode or degrade itsperformance.

In the context of the present invention, the term catholyte is definedas electrolyte of the electrochemical cell structure that is in contactwith the cathode. Furthermore, by virtue of the protected anodearchitecture, the catholyte is further defined as not being in contactwith the active metal anode. Accordingly, the catholyte, as definedhere, is part of the environment external to the protected anodecompartment. The catholyte may comprise a solid, liquid or gas.Moreover, the catholyte may comprise electrochemically activeconstituents such as but not limited to aqueous depolarizers, seawater,dissolved oxidants such as oxygen dissolved in aqueous or non-aqueous,reversible reduction/oxidation (redox) couples such as vanadium redoxspecies used in flow cell batteries, and/or particulate redox couples.

The electrochemical cell structures of the present invention compriseprotected anode architectures, catholytes and cathode structures. Thecathode structure and catholyte are external to the anode compartment ofthe protected anode architecture. In combination the cathode structureand catholyte may be considered as part of a cathode compartment or acathode environment whereby electrochemically active cathodeconstituents undergo reduction and oxidation. The electrochemicallyactive cathode constituents may be part of the catholyte, cathodestructure or a combination of both. The electrochemical reduction andoxidation reactions of the electrochemically active constituents takeplace on or within the cathode structure. Accordingly, the cathodestructures, in the context of the present invention, comprise anelectronically conductive component, and may additionally comprise anionically conductive component, and an electrochemically activecomponent.

While the cathode active constituents may in part or in whole becontained within the catholyte, the electrochemical redox reactions takeplace on or within the cathode structure. Accordingly, in some aspectsof the present invention the catholyte is retained, in part, inside thecathode structure. In other embodiments of the invention, the catholyteis retained, in part, inside a catholyte reservoir compartment. Thecatholyte reservoir compartment may be partially or fully locatedbetween the cathode structure and the protected anode architecture. Itmay also be located, in part, inside a separate reservoir containerspatially removed from the region between the cathode structure and theprotected anode architecture, such as in the case of a redox flow cell.In such a configuration some of the discharge product could be storedexternal to the cell for disposal or charge.

A cross-sectional depiction of a general electrochemical cell structure1350 of the present invention is illustrated in FIG. 13. The cellstructure comprises a protected anode architecture comprising an activemetal anode 1300 having a first and second surface enclosed inside ananode compartment 1330; and a cathode compartment 1340 comprising acathode structure 1312 and an optional catholyte reservoir 1316 locatedbetween the cathode structure and the surface of the anode protectivemembrane architecture 1302. The cathode structure 1312 comprises anelectronic conductor, catholyte and may also comprise electrochemicallyactive material. The catholyte reservoir, optional, comprises catholyteand may include an optional separator material as well, such as amicroporous Celgard or a porous cloth. The catholyte may be any suitableelectrolyte material including aqueous or non-aqueous and may furthercomprise electrochemically active species dissolved or suspended in theelectrolyte. Adjacent to the first surface of the anode is theprotective membrane architecture 1302, and adjacent to the secondsurface of the anode is the anode backplane 1306. The anode and cathodecompartments are enclosed in a battery container comprising a top lid1324, and container wall 1326, and a bottom base, which in theembodiment illustrated serves as the anode backplane.

The protected anode architectures of the present invention physicallyand chemically isolate the active metal anode from the cathodeenvironment, effectively creating an anode compartment and a cathodecompartment (sometimes also referred to as the cathode environment) thatcomprises a cathode structure and catholyte. Accordingly, the presentinvention enables a great degree of flexibility in the choice ofelectrochemical cell structures, as the components in the anode andcathode compartments can be chosen and optimized independent of eachother. For example, the protected anode architectures of the presentinvention enable active metal battery cells to be used in cathodeenvironments that are otherwise corrosive to the anode.

The effective isolation of the anode and the cathode provides a greatdeal of flexibility in the choice of catholytes. While the catholytesuseful in the present invention may comprise a solid, liquid or gas,they are primarily liquid phase. In many aspects of the presentinvention the catholytes may comprise electrochemically active redoxconstituents such as, but not limited to, redox active liquids such aswater, seawater, oxyhalides such as SOCl₂, dissolved redox species suchas transition metal chlorides or bromides, dissolved oxidants such asoxygen dissolved in aqueous or non-aqueous, reversible redox couplessuch as vanadium redox species used in flow cell batteries, and/orparticulate redox couples suspended in a carrier fluid.

Furthermore, since the protected anode is completely decoupled from thecatholyte, so that catholyte compatibility with the anode is no longeran issue, solvents and salts which are not kinetically stable to theactive metal anode (e.g., Li, Na, LiC₆, and the like) can be used. Theprotected anode architecture enables a wide range of possiblecatholytes, including ionic liquids, for use in battery cells thatincorporate cathode structures comprising intercalation cathodes likeLiFePO₄, and LiV₂PO₄ and other high voltage cathodes. Moreover, thechoice of anolyte solvents and salts in contact with the active metalanode or active metal intercalating anode such as a lithiated carbonanode is broadened as the chemical stability of the anolyte with thecathode structure is de-coupled.

In one embodiment of the invention, the catholyte is designed to flushthrough the cathode compartment/region thereby expelling dischargeproduct and re-supplying oxidant, for example, as would be embodied in ametal/seawater battery cell immersed in the ocean or an electrochemicalflow cell structure.

In other embodiments the invention relates to electrochemical cellstructures having aqueous cathode environments such as those ofmetal/air cells, metal/seawater cells, metal/hydride cells, such as aredescribed in commonly assigned co-pending published US Applications US2004/0197641 and US 2005/0175894.

The cathode structure of a battery cell comprising protected anodearchitectures in accordance with the present invention may have anydesired composition and, due to the isolation provided by the protectedanode architecture, is not limited by the active metal anode or anolytecomposition. In particular, the cathode structure may incorporatecomponents which would otherwise be highly reactive with the anodeactive metal.

The protected anodes described herein enable the efficient operation ofactive metal (e.g., Li, Na) batteries and other electrochemical cellsthat are open to their environment such as metal/air and metal/waterbatteries having aqueous constituents in their cathode compartments,such as Li/seawater cells and Li/air cells. Generally, such cells have acathode compartment comprising a catholyte and a cathode structure whichfurther comprises an electronically conductive component, an ionicallyconductive component, and an electrochemically active component, with atleast one of these cathode structure components having an aqueouscomposition or constituent. These cells have greatly enhancedperformance characteristics relative to conventional cells. As describedfurther below, the cells have a broad array of potential implementationsand applications.

While these cell types operate according to different electrochemicalreactions and have electrochemically active components in their cathodesdrawn from different states (primarily liquid, gas and solid states,respectively), each of these cell types includes the common feature ofan aqueous constituent for Li ion transport on the cathode side of thecell. The decoupling of the anode and cathode by the protective membraneallows for the fabrication of this powerful new type of battery or otherelectrochemical cell.

Metal/Air Cells

The protected anode architectures and associated arrays of the instantinvention have particular utility in metal air batteries such as Li-air(or Na-air). These cells have an active metal, e.g., alkali metal e.g.,lithium, anode that is encapsulated by the protective membranearchitecture in contiguity with the compliant seal structure and anodebackplane and a cathode with air as the electrochemically activecomponent. While not so limited, the electrochemical reaction betweenthe Li ions from the anode and the air is believed to be described byone or more of the following reaction schemes:

Li+½H₂O+¼O₂═LiOH

Li+¼O₂=½Li₂O

Li½O=½Li₂O₂

Thus both moisture (H₂O) and oxygen in the air are participants in theelectrochemical reaction.

Alkali metals such as Li corrode in aqueous solutions. Accordingly, anypart of the active metal anode (e.g., Li or Na) that is not covered bythe protective membrane architecture should be sealed off from the aircathode environment. The protected anodes of the present inventionprovide such an enclosure in the form of an hermetically sealed anodecompartment that encapsulates the active metal anode by a continuity ofthe solid electrolyte and the substantially impervious compliant sealstructure and anode backplane. Moreover, the flexibility of thecompliant seal structure provides a mechanism to minimize the volume ofthe anode compartment during charging and discharging whileconcomitantly allowing for optimization of the volume of the entirebattery cell. For example, during discharge of a Li/air cell the anodethickness decreases as Li leaves the anode compartment, while thecathode/aqueous electrolyte volume tends to increase as a result of theformation of lithium hydroxide. Accordingly, during discharge as theanode compartment shrinks, the associated volume in the remainder of thecell, cathode compartment, gets larger and is able to incorporate thedischarge product as it is formed. If not for the compliant sealstructure not only would there be lost space in the anode compartmentduring discharge, the cathode compartment would need to be designed toaccommodate the entirety of the cathode volume expansion. The compliantseal structure thereby minimizes the volume (weight) of the entireelectrochemical cell structure. The extra space needed for the LiOHwould have to be entirely compensated for by extra volume of the cathodecompartment prior to cell operation, if not for the compliancy of theseal structures of this invention.

An example of a metal/air battery comprising a protected anode inaccordance with the instant invention is a Li/air battery cell.Referring to FIG. 9A, there is illustrated a cross sectional depictionof a specific implementation of such a lithium/air 950 cell inaccordance with the present invention. The battery cell 950 comprises acell container comprising a top lid 924 having ambient air access holes,a bottom base 906 (which is the anode backplane in this embodiment) anda container wall 926. The metal air battery cell 950 further comprises aprotective anode architecture. The protective anode architecturecomprising a protective membrane architecture 902, an anode backplane906, and a compliant seal structure 904. When joined and sealed, theprotective membrane architecture 902, anode backplane 906, and compliantseal structure 904 effectively form a hermetic anode compartment, 930,that encloses the active metal anode 900. In this embodiment the anodebackplane 906 is a substantially impervious, electronically conductivematerial that provides structural support in the form of the bottom baseof the cell container, it also provides current collection and terminalconnection for the protected anode architecture.

In the case of the instant embodiment, the compliant seal structure 904is molded into a preformed frame having a first 932 and second step 934.The inner surface of the first step 932 is bonded to the protected anodearchitecture 902. The inner surface of the second step 934 is bonded tothe anode backplane 906. While the inner surface of the compliant sealstructure is exposed to the environment inside the anode compartment930, the outer surface of the compliant seal structure is exposed to theenvironment of the cathode compartment 940, which further comprises acathode structure 912 and a catholyte reservoir 916 comprisingcatholyte.

A preferred compliant seal structure of the instant embodiment is amulti-layer laminate comprising a plurality of layers. A top polymericlayer, that forms the outer surface of the laminate and is chemicallyresistant to the environment of the cathode compartment (e.g., PET,PTFE, etc); at least one of a middle barrier layer comprising a metalfoil such as an aluminum foil, and a bottom polymeric layer that formsthe inner surface of the laminate and is chemically resistant to theelements of the anode compartment, including in some aspects a liquid orgel anolyte, and is also heat-sealable (e.g., PE, PP, ionomers andionomer resins commonly referred to as Surlyn). In this embodiment, thecompliant seal structure is bonded by thermal compression to theprotective anode architecture and anode backplane.

The anode backplane 906 provides the bottom base for the battery cellcontainer. In this embodiment the bottom base of the battery containercan be an electronically conductive material, such as a stainless steelalloy or nickel, suitably thick to provide a substantially imperviousbarrier (e.g., about 200 microns), current collection and a terminalconnection.

The battery cell also includes a cathode compartment 940 comprising acathode structure 912 and a catholyte reservoir 916. The cathodestructure 912 (sometimes referred to as an air electrode) comprises anelectronically conductive component, an aqueous or ionomeric ionicallyconductive component, and air as an electrochemically active component.The air electrochemically active component of these cells includesmoisture to provide water for the electrochemical reaction. Sincemetal/air batteries obtain the cathode active reactant from the ambientenvironment, the volumetric and gravimetric energy densities are veryhigh. The high energy density of metal/air batteries makes themattractive for a wide variety of applications where weight and size area premium.

The cathode structure 912 includes an electronically conductivecomponent (for example, a porous electronic conductor, an ionicallyconductive component with at least an aqueous constituent, and air as anelectrochemically active component. It may be any suitable airelectrode, including those conventionally used in metal (e.g., Zn)/airbatteries or low temperature (e.g., PEM) fuel cells. Air cathodes usedin metal/air batteries, in particular in Zn/air batteries, are describedin many sources including “Handbook of Batteries” (Linden and T. B.Reddy, McGraw-Hill, NY, Third Edition) and are usually composed ofseveral layers including an air diffusion membrane, a hydrophobic PTFE(e.g., Teflon®) layer, a catalyst layer, and a metal electronicallyconductive component/current collector, such as a Ni screen. Thecatalyst layer also includes an ionically conductivecomponent/electrolyte that may be aqueous and/or ionomeric. A typicalaqueous electrolyte is composed of KOH dissolved in water. An typicalionomeric electrolyte is composed of a hydrated (water) Li ionconductive polymer such as a per-fluoro-sulfonic acid polymer film(e.g., du Pont NAFION). The air diffusion membrane adjusts the air(oxygen) flow. The hydrophobic layer prevents penetration of the cell'selectrolyte into the air-diffusion membrane. This layer usually containscarbon and Teflon particles. The catalyst layer usually contains a highsurface area carbon and a catalyst for acceleration of reduction ofoxygen gas. Metal oxides, for example MnO₂, are used as the catalystsfor oxygen reduction in most of the commercial cathodes. Alternativecatalysts include metal macrocycles such as cobalt phthalocyanine, andhighly dispersed precious metals such at platinum and platinum/rutheniumalloys. Since the air electrode structure is chemically isolated fromthe active metal anode, the chemical composition of the air electrode isnot constrained by potential reactivity with the anode active material.This can allow for the design of higher performance air electrodes usingmaterials that would normally attack unprotected metal electrodes.

The catholyte reservoir 916, contains aqueous catholyte and in theinstant embodiment is located between the cathode structure 912 and theprotective membrane architecture 902. The catholyte reservoir mayinclude a porous support material such as a zirconia cloth from ZircarProducts, Inc. filled with catholyte solution. The catholyte may beformulated with neutral (LiCl) basic (KOH) or acidic (NH₄Cl, HCl, etc)solutions. For example, a 0.5M NH4Cl+0.5M LiCl. The catholyte reservoirmay further comprise an optional separator material (not shown) may beprovided between the catholyte reservoir and the protective membranearchitecture such as a polyolefin such as polyethylene or polypropylene,for example a CELGARD separator.

The Li/air cells of the present invention may be either primary orsecondary cells.

The battery enclosure includes a top lid 924 having air access holes forthe inlet of ambient air and moisture into the cathode compartment.Optionally, a spring 922 may be incorporated between the top lid of thebattery container and the cathode compartment to maintain contact ofinternal components during discharge and charge. The battery containerwall 926 surrounds the battery cell and is joined on one of its openfaces to the bottom base of the container and on its opposing open faceto the top lid 924. In the instance whereby the bottom base is aterminal connector for the anode and the top lid is in electroniccontinuity with the cathode, the surrounding wall should be anelectronic insulator so as not to short circuit the battery.Alternatively, any other suitable material or technique to avoidelectronic contact between the top lid and the bottom base can be used,and such materials and techniques are well known to those skilled in theart, such as providing an insulating gasket between either the containerwall and the top lid or the container wall and the bottom lid, or both.

It is an aspect of the present invention that the compliant sealstructures allow for minimization of wasted volume in the battery. Aninternal seal in an electrochemical cell structure can adversely affectthe energy density of a battery cell in that as the battery isdischarged, the active metal anode thickness decreases leaving aninternal void in the battery at the same time products formed in thepositive electrode lead to a volume expansion; so the battery design,including the size of the battery cell container, needs to include extraspace in the positive electrode compartment to accommodate thatexpansion. In one embodiment, it is a feature of the present inventionthat during charge and discharge, as the active metal anode expands andshrinks, the compliant seal structure deforms in such a manner as toalter the thickness of the anode compartment. This allows the protectivemembrane architecture and anode backplane to maintain physicalcontinuity with the surface of the active metal anode and mitigates theformation of voids in the anode compartment. Furthermore, because thevoid volume is taken up by the anode compartment as it shrinks duringdischarge, the extra space subsequently formed in the remainder of thebattery cell can be used to accommodate the expansion of the cathodestructure. This results in a compact battery cell design. Thus,according to this aspect of the instant invention, the compliant sealstructure is used to minimize volume in the battery container, therebymaximizing the energy density of the battery.

As illustrated in FIGS. 9A and 9B, during discharge of a Li/air galvaniccell, the Li anode 900 supplies a source of lithium ions to the reactionphysically manifested by the disappearance of the lithium metal foil,concomitant with the production of lithium hydroxide. In the Li/air cell950, the product LiOH is stored in the cathode compartment 940, leadingto an expansion of volume with proceeding cell discharge. As thedischarge progresses the presence of the compliant seal structure 904allows the expansion of the cathode compartment 940 volume to becompensated by the decrease in volume of the anode compartment.

FIGS. 9A and 9B qualitatively illustrate the volumetric changes thattake place in the Li/air cell 950 during operation (discharge andcharge). FIG. 9A shows the cell 950 in the fully charged state and FIG.9B shows the cell 950 in a state of intermediate discharge. As the Limetal thickness shrinks during discharge the compliant seal structure904 deforms in such a manner as to provide the protective membranearchitecture 902 a range of motion for it to follow the first surface ofthe Li metal foil 900. Furthermore, in certain embodiments, the anodebackplane 906, which forms the bottom base of the battery cellcontainer, is prevented from moving because it is anchored to thebattery container. By this expedient, as the anode thickness shrinks orexpands, respectively during discharge or charge, it is the protectivemembrane architecture that under an external force moves/translates asit follows the first surface of the anode, while the backplane, beingfixed to the container, is substantially immobilized. In certainembodiments, the force exerted on the membrane architecture is broughtabout by a volume expansion of the cathode compartment which can beeffected by the formation of discharge product (e.g., lithium hydroxide)in the catholyte and/or by absorption of water from the air, and/orbrought about or augmented by a spring 922 or some other cell componentor phenomena. Ergo, in this embodiment, it is the traversal of theprotective membrane architecture, as it moves along with the anode'sfirst surface, which leads to the concomitant decrease in theheight/thickness of the anode compartment.

The compliant seal structure 904 of the present invention provides alarge range of motion as Li/air batteries are generally high capacitycells that incorporate a relatively thick active metal anode. The rangeof motion corresponds to about 100% of the battery rated depth ofdischarge. Typically the Li metal foil anodes are at least 10 microns,more preferably at least 50 microns, even more preferred is greater than100 microns. In some aspects of the present invention the range ofmotion is greater than 250 microns, greater than 500 microns, greaterthan 1 centimeter, or even as much as 10 cm, or more.

In another embodiment of the present invention, the metal/air batterycell is double sided in the sense that it is able to capture ambient airand moisture from both planar surfaces. Compared to a single sided cell,the apparent active area is doubled. Referring to FIG. 10, adouble-sided metal air battery cell 1050 is illustrated in across-sectional depiction comprising a protected anode architecture, acathode compartment and a battery casing. The protected anodearchitecture comprises an active metal anode 1000 with a first andsecond surface. The first surface is adjacent to the protective membranearchitecture 1002. The second surface of the active metal anode isadjacent to the anode backplane 1006, which in this embodiment is asecond protective membrane architecture. A terminal connector 1010joined to a current collector 1008 that is embedded within the activemetal anode, providing both current collection and an electronicterminal. In one aspect the current collector 1008 and terminalconnector may comprise nickel metal, about 50 micron thick and arejoined by resistance welding.

Each of the ion membrane architectures 1002 and 1006 of the instantembodiment are bonded to separate compliant seal structure components1004 and 1005. In the instant embodiment, the compliant seal structureis referred to herein as being configurationally symmetric in that thereare two mirror planes that run through the middle of the anode layer:one that is perpendicular and the other that is parallel with the firstand second surfaces of the anode; these minor planes are referred toherein more simply as the perpendicular mirror plane and the parallelmirror plane. The compliant seal structure components are molded intopreformed frames with top and bottom steps. As described above the firststep of each compliant seal structure component (1004/1005) is bonded toits respective protective membrane architecture (1002/1006). The secondstep of each compliant seal structure component 1004 and 1005 are bondedto each other to form the hermetic enclosure that is the anodecompartment of the double-sided protected anode architecture. In oneembodiment the compliant seal structures comprise a low meltingtemperature thermoplastic (e.g., PE, PP, Surlyn, etc.) and are bonded totheir protective architectures and to each other by a heat seal.

Adjacent to the outer surface of the first protective membranearchitecture 1002 and the second protective membrane architecture 1006are cathode compartments 1040 and 1041 that respectively comprise acatholyte reservoir 1016 and 1017 and a cathode structure 1012 and 1013.The cathode structures 1016, 1017 and catholyte reservoirs 1012, 1013are similar to those described in the above embodiment.

The battery cell container comprises a top lid 1024, a bottom base 1034and a container wall 1014. Both the top lid 1024 and the bottom base1034 contain air access holes to provide ambient air and moisture toenter into the top and bottom cathode compartments. The container wallis typically an electronic insulator. The top and bottom lids mayprovide terminal electronic connections for their respective cathodestructures. Accordingly, the top and bottom lids may be comprise asuitable metal, such as a stainless steel alloy or nickel. Optionally, aspring 1022 is located between the top lid 1024 and the cathodestructure 1012 as well as between the bottom base 1034 and its adjacentcathode structure 1013.

The current collector 1008 for the active metal anode 1000 is joined toa terminal connector 1010. The terminal may be attached to the currentcollector or the active metal material of the anode by any of a numberof well-known methods such as but not limited to soldering, physicalpressure, ultrasonic welding, and resistance welding. The currentcollector may bisect the active metal material, as shown, oralternatively, may contact it or partially penetrate it depending uponthe design choice of the manufacturer.

The terminal tab extends to the outside of the anode compartment and inone aspect of the invention it exits the anode compartment at thejunction where the first and second compliant seal structures 1004/1005are bonded together. In the instance whereby the compliant sealstructures 1004 and 1005 are a multi-layer laminate comprising aheat-sealable thermoplastic, the terminal tab 1010 is encapsulated bythermal compression.

In this embodiment, the terminal tab exits the anode compartment, butshould be electronically insulated around its surface to avoidinternally short circuiting the battery cell via contact with catholyte.Accordingly the terminal tab is wrapped or embedded inside aninsulating, chemically resistant material such as PP, PE or PTFE overthe length of the terminal tab that remains inside the battery cellcontainer.

In accordance with the instant invention, the compliant seal structure,which comprises compliant seal structure components 1004 and 1005),adapts its shape during discharge in order to allow both the first andsecond membrane architectures to move toward each other duringdischarge, and to move away from each other during a subsequent charge.In this embodiment, the compliant seal structure is configurationallysymmetric and affords both membranes substantially the sametranslational range of motion, albeit in opposite directions.

Alternatively, protected anode architectures in accordance with theinstant invention can have asymmetric compliant seal structures. Theasymmetry can arise from the configuration of the structure or itsgeometry (e.g., thickness); asymmetry can also be imparted to thestructure by a materials variation. The embodiment illustrated in FIG.14 is that of a double-sided protected anode architecture 1450 having anasymmetric seal structure that comprises a first seal structurecomponent 1404 having a double step configuration and a second structurecomponent 1405 having a flat configuration. The first component 1404 isbonded to the first protective membrane architecture 1402, and thesecond component 1405 is bonded to the anode backplane 1406, which inthis embodiment is the second protective membrane architecture. Theanode 1400 is encapsulated on its first surface by the first protectivemembrane 1402 and on its second surface by the second protectivemembrane 1406. The two component structures (1405 and 1405) are bondedtogether, thus forming the compliant seal structure. The seal structure,while having a perpendicular mirror plane is configurationallyasymmetric in that it does not have a horizontal minor plane through themiddle of the anode. The asymmetry alters the manner in which thecompliant seal structure deforms or adapts its shape in response toanode thickness changes during discharge or charge. By this expedient,the range of motion of one or the other of the anode backplane or theprotective membrane architecture can be adjusted. For instance, in theinstant embodiment, the deformation of the compliant seal structureduring discharge favors translation of the first protective membranearchitecture over that of the second. So the thickness decrease of theanode compartment is effected more so by the translation of the firstrather than that of the second protective membrane architecture.

In an alternative embodiment, illustrated in FIG. 11, the batterycontainer has a button cell format. The metal/air button cell 1150 has atop lid 1124 and a bottom base 1126. The top lid contains air accessholes and is joined to the bottom base by a fixed seal insulator 1128.The protected anode architecture includes an active metal anode 1100e.g., lithium, having a first and second surface. The second surface ofthe Li is adjacent to the anode backplane 1106, which in this embodimentis the bottom base of the button cell container. In this embodiment, theanode backplane is affixed to the cell container (a positionally fixedrigid member), and as such is prevented from moving as the anodethickness changes during cell operation. By this expedient, the changein the anode compartment thickness, as a result of cell discharge isbrought about entirely by the translation of the protective membranearchitecture—it moving along with the first surface of the anode.Encapsulating the first surface of the Li is a protective membranearchitecture 1102. The compliant seal structure comprises a flexibleframe material formed to have a first and second step. The protectivemembrane architecture is bonded to the first step of the compliant sealstructure. Different than that described in previous embodiments, thesecond step of the compliant seal structure is bonded to a fixed sealjoint that is capable of forming an hermetic compression seal betweenthe top lid and bottom base of the container. Fixed seal insulators areknown in the art, particularly suitable fixed seal insulators arefluoro-elastomeric co-polymers such as those developed under the tradename of Viton. Accordingly, the anode compartment is sealed off from thecathode compartment 1140 of the cell by the crimp/compression seal ofthe fixed seal joint. The cathode compartment 1140 comprises a cathodestructure 1112 and a catholyte reservoir as described above. Similar tothe above embodiments there is an optional spring 1122.

The protected anode architectures of the instant invention are usefulfor almost any battery cell system that contains catholyte or cathodestructures that are unstable against an active metal anode. Thisincludes aqueous catholytes as well as non-aquoues catholytes such asthose useful for improved performance of ion intercalating batterychemistries, such as those comprising cathode structures comprisingtransition metal oxides and transition metal phosphates.

In another embodiment of battery systems in accordance with the presentinvention, electrochemical cell structures comprise catholyte that maybe flushed through the cathode compartment/region. For example, in aredox flow cell, the catholyte comprises active metal species that maybe flowed to the cathode structure in order to undergo reduction, andsubsequent to reduction flushed out of the cathode compartment/region toa separate reservoir for disposal or oxidation back to its originalcharged state. Alternatively, the reduced species may be flowed backthrough the cathode compartment/region for oxidation of theelectrochemically active species in the catholyte and as means to chargethe active metal anode.

In another embodiment, seawater is the catholyte. The compliant sealstructures of the instant invention yield significant benefit formetal/seawater batteries including Li/seawater (or sodium/seawater).Such batteries have exceptionally high energy density (Wh/l) andspecific energy (Wh/kg) since seawater serves as both the aqueouselectrolyte and oxidant, and does not have to be carried in the batterypack. In addition to providing hermetic protection, the use of thecompliant seal structures to enclose the protected anode compartmentallows the hydrostatic pressure of the ocean to compress the anode asdischarge of the negative electrode proceeds, facilitating uniformpressure of the solid electrolyte plate against the active metal of theanode which is important to achieve full utilization of the activemetal.

Embodiments of metal seawater cells 1250 with a protected anode of thepresent invention is illustrated in FIGS. 12A and 12B. In FIG. 12A theprotected anode architecture is double sided. In FIG. 12B the protectedanode architecture is single sided.

Referring to FIG. 12A, the protected anode is fully described in thedescription of the embodiment illustrated in FIG. 4 for a double-sidedprotected anode. Briefly the protected anode architecture comprises anactive metal anode 1200, having a current collector 1208 embedded insideand a terminal connector 1210 joined to the current collector. Theactive metal anode 1200 has a first and second surface. Each surface isadjacent to a protective membrane architecture 1202 and 1206 (anodebackplane) The compliant seal structure components 1204 and 1205 arebonded to their respective protective membrane architectures 1202 and1206 and to each other to form the anode compartment 1230. In theseawater battery cell, adjacent to each surface of the protectivemembrane architecture is a cathode structure 1212 that provideselectrochemical reduction of the electrochemically active oxidants inthe seawater. The seawater catholyte 1216 exists in the region of thecathode compartment between the cathode structure 1212 and theprotective membrane architecture 1202 and 1212. Typically, seawatercontains dissolved oxygen, in which case the cell potential will be amixed potential due to the lithium/water and lithium/oxygen reactions.The battery cells incorporating the protected anode architectures of thepresent invention are designed such that the reduction products, such asactive metal hydroxides, do not remain in the cathodecompartment/region. The cathode structures of the instant embodimentcomprise an electronically conductive support structure that isgenerally porous to allow fluid to flow through. The cathode comprises asuitable electronically conductive material that does not corrode inseawater, such as a titanium screen or mesh that allows for seawater toflow through its structure.

The suitability of seawater as an electrolyte enables a battery cell formarine applications with very high energy density. Prior to use, thecell structure is composed of the protected anode and the porouselectronically conductive support structure (electronically conductivecomponent), such as a titanium screen. When needed, the cell iscompleted by immersing it in seawater which provides theelectrochemically active and ionically conductive components. Since thelatter components are provided by the seawater in the environment, theyneed not transported as part of the battery cell prior to it use (andthus need not be included in the cell's energy density calculation).Such a cell is referred to as an “open” cell since the reaction productson the cathode side are not contained. Such a cell is, therefore, aprimary cell.

In active metal/Seawater batteries of the instant invention, such asLi/Seawater or Na/Seawater, it is generally hydrostatic pressure thatsupplies the external force against the protective membrane architectureand anode backplane which causes either or both to move along with theanode surface which they respectively encapsulate. Protected anodearchitectures such as those previously described herein for Li/Airbattery embodiments can generally be usefully employed in a Li/Seawaterbattery. This includes single and double sided protected anodearchitectures, having symmetrical or asymmetrical compliant sealstructures.

In various embodiments, the Li/Seawater batteries of the instantinvention have utility for use in the ocean/sea, and in certainapplications at considerable depths. The hydrostatic pressure of theocean increases at a rate of 1 atmosphere per every 10 meters, so at adepth of 3000 meters the pressure is about 4200 psi. In another aspectof this invention, in order to survive the hydrostatic pressure of theocean, particularly at depth, it is preferable that the anodecompartment should be filled with an anolyte (incompressible fluid; thisminimizes or eliminates void space in the anode compartment. Suitableanolytes useful for filling the anode compartment include thosedescribed above for use as anolyte in protective membrane architectures.

Another protected anode architecture embodiment that is particularlysuitable for high capacity (Ah) Li/Seawater battery cells is illustratedin FIG. 15A-C.

Referring to FIG. 15A, the Li/Seawater battery cell 1550 is shown in itsfully charged state. The cell 1550 comprises a protected anodearchitecture 1520 and a cathode structure 1512 which provideselectrochemical reduction of seawater oxidants. Cathode structuresusefully employed in a Li/Seawater battery have already been describedabove.

The protected anode architecture 1520 comprises a lithium metal anode1500 having a first surface and an opposing second surface (e.g., a rodof lithium). Referring back to FIG. 15A, the first surface of the anodeis encapsulated by a protective membrane architecture 1502.

In accordance with this embodiment the compliant seal structure 1504 isjoined to the protective membrane architecture 1502 via a rigid member1505. The rigid member 1505 forms a portion of the anode compartmentenclosure, and it is joined to an edge or outer peripheral surface ofthe protective membrane 1502, for instance by using a discrete sealantsuch as an epoxy. In certain embodiments, the rigid member ispositionally fixed and prevents translation of the protective membranearchitecture during discharge. The rigid member can be, for instance, inthe form of an annulus (e.g., square or circular), hollow tube orcylinder; the wall thickness of which should be large enough to providethe necessary mechanical strength so that during discharge the memberremains rigid. The rigid member should also be substantially chemicallyresistant in contact with seawater. Suitable materials for the rigidmember include metals such as stainless steel, aluminum and the like oreven plastics such as plexiglass or high-density polyethylene. Moreover,a chemically resistant coating can be applied to the outer surface ofthe rigid member to enhance its chemical stability in contact withseawater.

The compliant seal structure 1504 is joined to the rigid member 1505(e.g., by a discrete sealant such as an epoxy). The compliant sealstructure can be molded or fabricated into a pre-formed shape, forinstance into a flexible cylindrical vessel or tube having an open and aclosed end. Moreover, in accordance with the instant embodiment, theseal structure is pre-formed to contain a fold 1522 that can be formedfor instance by folding the seal material onto itself. The closed end ofthe compliant seal structure encapsulates the second surface of theanode, and thus constitutes the anode backplane 1506 or a componentthereof. Accordingly, the compliant seal structure 1504 and the anodebackplane 1506 are formed by a single contiguous piece of material suchas a polymer or laminate. The fold 1522 is configured such that itsvertex is directed away from the anode backplane 1506, substantially ina direction opposite the anode. The fold 1522 can serve to influence themanner in which the complaint seal structure 1504 deforms in response tothe translation of the anode backplane 1506 during discharge.

Suitable materials for the compliant-seal-structure/anode-backplanecomponent include polymers or laminates as described above for compliantseal structures, including ethylene propylene diene monomer rubber(EPDM). The compliant seal 1504 may further comprise a barrier materiallayer, such as a metal layer, to improve its impermeability toconstituents of seawater. In accordance with the instant embodiment, theanode backplane 1506 may further comprise an optional anode backplanesupport component, not shown, such as a copper sheet that can functionas both a current collector and as a mechanical support for the anode.For providing electronic current through the anode compartment, aterminal connector, also not shown, can be attached to the currentcollector or directly to the lithium, the connector exiting the anodecompartment, for instance, through a sealed port in the anode backplane1506.

In accordance with the instant embodiment illustrated in FIG. 15A, andas described above, depending on depth, the hydrostatic pressure in theocean can be large, so in order to survive high pressures, the anodecompartment can be filled with an incompressible fluid, such as a liquid(e.g., liquid anolyte or a non-aqueous solvent). In the instance wherethe protective membrane architecture has a liquid anolyte interlayer, itis preferable that the incompressible fluid used to fill the anodecompartment has nominally the same composition as the interlayeranolyte, because the two liquids might eventually mix with each other,perhaps in fabrication or at some point during device operation. Incertain embodiments, particularly when the protected anode architecture1520 is deployed at some considerable ocean depth, any open spaces inthe anode compartment (as shown at 1510) are filled with anincompressible fluid, such as a liquid anolyte. Moreover, theincompressible fluid (e.g., anolyte or a non-aqueous solvent) can beusefully employed as a liquid layer situated between the anode 1500 andthe compliant seal structure 1504 in order to facilitate the ease withwhich the compliant seal structure 1504 deforms as the anode backplane1506 follows the second surface of the anode 1500 during discharge.

In FIGS. 15B and C the protected anode architecture 1520 is shown atvarious stages of discharge in a partially discharged state. In certainembodiments, the rigid member 1505 is positionally fixed, so only thebackplane 1506 is able to translate under the influence of hydrostaticpressure. As the anode backplane 1506 moves along with the secondsurface of the anode during discharge, the compliant seal structure 1504continues to fold onto itself. In this way, the compliant seal structuredoes not crinkle and bunch up in front of the backplane where it (thecrinkles) can potentially impede backplane translation. By thisexpedient, the protected anode architecture 1520 is able to provide asignificant range of motion for the anode backplane 1506 tomove/translate along with the anode's second surface. In some aspects ofthe invention this range of motion can be greater than 1 cm, preferablygreater than 10 cm, and more preferably greater than 50 cm, and evenmore preferably greater than 100 cm.

Referring back to FIG. 15A, optionally, the protected anode architecture1520 may be held in a retaining case 1530 that is open to the seawater.The retaining case can be joined to the rigid member, and the case isgenerally adjacent to and surrounds most of or a portion of the lateralsurface of the anode compartment, and as shown in FIG. 15A, it is alsoadjacent to the anode backplane. However, the retaining case should notimpede the electrochemistry which takes place between the surface of theprotective membrane 1502 and the cathode 1512. In the instant embodimentillustrated, the retaining case is joined to the rigid member, forinstance by an epoxy seal or a weld. In certain embodiments, the casing1530 and the rigid member 1505 may be formed from a single contiguouspiece of material. The retaining case 1530 is open to the seawaterenvironment at least through an inlet port 1508. Placing the protectedanode architecture within such a retaining case 1530 provides bothmechanical support and some physical protection against damage thatmight be incurred during device deployment and/or operation in a dynamicseawater environment. The case 1530 also provides a mechanism tominimize damage that might ensue if the anode compartment is everbreached. Because the casing 1530 is only open to seawater via the inletport 1508, the flow of seawater into the casing is hindered, so if aseal breach takes place there is only a limited amount of seawater thatis immediately available to react with that lithium which might beexposed by a breech. By this expedient the adverse reaction between theseawater and exposed lithium will be slowed down and possibly evenmitigated in a short time.

This embodiment is particularly useful for achieving full utilization ofanodes with a thickness greater than about 1 cm, and particularly foranodes having a thickness of 10 cm or more. In this embodiment, as theanode is discharged, the backplane moves with the second surface of theanode in a direction toward the protective membrane, as the compliantseal structure deforms by continuing to fold onto itself in a directionaway from the backplane. By this expedience, the compliant sealstructure does not bunch/crinkle up on itself in front of the backplane,so thick lithium anodes can be discharged until fully exhausted.

In accordance with the present invention, Li/Seawater batteries of theinstant invention having protected anode architectures can deliver veryhigh energy density because they are able to discharge a great deal oflithium. In various embodiments, the Li/Seawater batteries of theinstant invention comprise lithium anodes that are at least 2 mm thick,more preferably greater than 5 mm, and even more preferably greater than10 mm. Moreover, in accordance with the present invention, the lithiumcan be fully utilized which is to say that the lithium can be dischargedto substantially 100% utilization. Accordingly, in various Li/Seawaterembodiments, the anode compartment can undergo a thickness decrease thatis equivalent to the starting thickness of the lithium anode prior todischarge. In various embodiments the anode compartment thicknessdecreases by more 2 mm, or more than 5 mm, or more than 10 mm.

Fabrication Methods

Methods suitable for fabricating protected anode architectures inaccordance are described in detail in the examples section whichfollows. Given this description and the structural and materialsparameters and guidance provided herein, the fabrication of protectedanode architectures, array and cells in accordance with the presentinvention would be readily apparent to one skilled in the art. A briefoverview is provided, with reference to a particular embodiment:

The compliant seal structures of the present invention may comprisediscrete elements or combinations of discrete elements each bondedseparately to the protective membrane architecture and anode backplane.Alternatively, in a preferred embodiment, the compliant seal structureis fabricated in the form of a unified article, such as a frame prior tobonding to the anode backplane and protective membrane architecture. Ina first operation, the compliant seal structure is preferably formedinto a frame of the desired configuration and including a window withinthe frame that provides an area for placing and bonding the protectivemembrane architecture(s). For example, a multi-layer laminate materialcan be molded as described in the examples, into a double stepconfiguration with a window cut-out. Preferably, the shape of the windowwill be the same as the protective membrane architecture. The inner edgearound the frame, which in the case of a double-step configurecorresponds to the first step, is bonded to the protective membranearchitecture. The first step is used as a bonding platform. The bond,for example, may be formed by a thermal compression of an integratedsealant or by the use of a discrete sealant. The protective membranearchitecture is bonded on its peripheral edge to the first step of thecompliant seal structure, thus filling the space within the window.Essentially, this forms the top half of the anode compartment. Theprotective membrane architecture is connected to the active metal anodeby methods that are fully described in commonly assigned published USApplications US 2004/0197641 and US 2005/0175894, cited and incorporatedby reference above. In the instances whereby the protective membranearchitecture comprises anolyte, the anolyte is preferably applied to theinterlayer after the solid-state membrane has been bonded to thecompliant seal structure; see Examples 2-4, below, for details. Theanode compartment is then fully enclosed, encapsulating the anode, bythe bonding of the outer edge (second step in a double-step configure)of the frame to the anode backplane. The protected anode architecturesof the present invention form fully enclosed structures that areisolated from the cathode environment (cathode compartment) and thus canbe utilized as an anode in a number of battery cells as described aboveand illustrated above.

Further details relating to fabrication are provided in the Exampleswhich follow.

EXAMPLES

The following examples provide details illustrating advantageousproperties and performance of protected anode architectures havingcompliant seal structures, components thereof, and battery cells inaccordance with the present invention. These examples are provided toexemplify and more clearly illustrate aspects of the present inventionand are in no way intended to be limiting.

Example 1 Demonstration of Effectiveness of Compliant Seal

A commercial multi-layer laminate material (MLLM) with the productspecification Laminate 95014 (manufactured by Lawson Mardon Flexible,Inc. in Shelbyville, Ky.) was used to make a compliant, hermetic seal toa lithium ion conducting glass-ceramic (GC) membrane. In this case, aswell as in all the examples described below, we used the GC membranes,developmental product AG-01, supplied to PolyPlus by the OHARACorporation. The ionic conductivity of the GC membrane was in the rangeof (1.0-1.5)×10⁻⁴ S/cm. The membrane was a 1″×1″ square with a thicknessof 150 micrometers.

The MLLM product Laminate 95014 has a thickness of 118-120 μm and ismade of:

-   -   PET—Polyethylene terephthalate, 12 μm    -   ADH—a two-part polyurethane adhesive    -   Aluminum foil, 32 μm    -   EAA—Ethacrylic acid (a primer for the aluminum foil; also        improves wetting between LDPE and PET)    -   PET—Polyethylene terephthalate, 12 μm    -   LDPE—Low density polyethylene    -   EAA—Ethacrylic acid

The LDPE heat-sealable bottom layer served for bonding of the GCmembrane surface with the multi-layer laminate. A square hole of 22mm×22 mm was cut into a sheet of laminate of about 5×6 inches. Bondingof the GC membrane surface with the bottom LDPE layer of the MLLM wasperformed using a Carver hydraulic press equipped with stainless steelhot plates. The width of the seal was approximately 1.7 mm. Thefollowing parameters were used for bonding a 1″×1″ GC membrane to thelaminate material: pressure of 250 kg, temperature of 100° C., pressingtime of 3 minutes.

The resulting laminate was then sealed with a heat sealer on three sidesto another laminate of similar dimensions (5″×6″) making an open-endedbag. The bag was then filled with approximately 40 ml of 1,2dimethoxyethane (DME), and the remaining side was heat-sealed to producea completely sealed bag. The human nose is quite sensitive to the smellof ethers such as DME, and can detect a few ppm. After sealing this bagin the manner described here, no scent of DME was detectable, and noloss of volume of this highly volatile solvent was detected, even afterabout one year of storage in the bag. Under unsealed conditions the sameamount of DME evaporates within a couple of hours. This experimentconfirms that the seal between the laminate material and the GC membraneis hermetic and does not deteriorate after long-term storage.

The following examples illustrate the performance of protected anodearchitectures comprising GC-protected Li anodes and compliant sealstructures and demonstrate strength and stability of variousmodifications of compliant seals.

Example 2 Testing of Double-Sided Protected Lithium Anode with CompliantSeal in Seawater Electrolyte

The same method and equipment as described in Example 1 were used tobond the GC membrane (substantially impervious, ionically conductivelayer) surface with the MLLM having a square hole of 22 mm×22 mm. Thewidth of the bond was approximately 1.7 mm. Two such structures werefabricated and then sealed together on three of their sides by bondingthe bottom LDPE layers of the MLLMs to each other. The impulseheat-sealer Model 14A/A-CAB (Vertrod Corp.) with modified jaws was usedfor this operation. The resulting open-ended bag had two GC platesbonded to the MLLMs.

A lithium electrode was fabricated in the dry room by pressing twosquare 22 mm×22 mm pieces of Li foil with a nominal thickness of 0.6 mm(FMC Lithium Inc.) on both sides of Ni foil current collector having thesame dimensions and a thickness of 50 μm. The pressing operation wasperformed in a die with polypropylene block using a pressure of 750 kgfor 3 minutes. A Ni strip with a width of 3 mm, a length ofapproximately 12 cm and a thickness of 50 μm served as an anode terminaltab. This tab was sandwiched between two 5 mm wide strips of the PETfilm (20 μm in thickness), while both of the tab's ends were leftexposed. The Ni foil and the PET films were sealed together with an LDPEglue. As a result, the tab was encapsulated with chemically stable andelectrically insulating materials. One of tab's ends was then welded tothe Ni current collector.

The Li electrode was wrapped with a 25 μm thick film of microporousCelgard 3401 separator. Then the Li electrode was placed into theopen-ended bag described above, such that the 22 mm×22 mm Li squareswere aligned with the 22 mm×22 mm areas of the GC plates not covered bythe bond on the outside of the bag.

The anode compartment was filled under vacuum with anolyte consisting ofnon-aqueous electrolyte comprising 1.0 M of LiClO₄ salt dissolved inpropylene carbonate. Here the non-aqueous electrolyte (anlolyte)impregnates the microporous Celgard 3401 separator. The anolyteimpregnated Celgard interlayer separates the Li metal surface from theGC membrane (solid electrolyte layer). The moisture concentration in thenon-aqueous electrolyte did not exceed 10 ppm. The open end of the bagwas then heat-sealed with a vacuum sealer Audionvac VM 101H.

The Ni tab exited the anode compartment between the two MLLMs. Thehermetic seal at the junction between the tab and the anode compartmentwas ensured by the heat-seal bond between the PET layers encapsulatingthe tab and the thermoplastic LDPE layers of the MLLMs. The resultinghermetically sealed anode compartment was approximately 40 mm×40 mm insize.

The protected anode with compliant seal was tested in a Li/waterelectrochemical cell with seawater electrolyte. The anode was completelyimmersed in a glass beaker containing 4 L of synthetic seawater (RiccaChemical Company) as catholyte. A counter electrode (cathode structure)was fabricated from a Ti Exmet 5Ti7-077FA in the form of a cylinder witha geometrical area of 240 cm² and was placed against the walls of thesame beaker, thus surrounding the anode.

During anode discharge the Ti cathode surface facilitated the cathodicreaction of electrochemical hydrogen evolution from seawater.

The cell also employed an Ag/AgCl reference electrode, which was locatedin seawater electrolyte near the anode and served for anode potentialmeasurements during discharge. The experimental values of the anodepotential versus Ag/AgCl were recalculated into the standard hydrogenelectrode (SHE) scale. The anode was discharged at a current density of0.5 mA/cm² of Li surface using Maccor battery tester.

The discharge curve is shown in FIG. 16. Comparison of available anodecapacity calculated from the weight of lithium foil placed in the anodecompartment and actual discharge capacity shows that discharge is 100%efficient. The entire amount of lithium was discharged from both sidesof the Ni current collector across the GC plates into the seawaterelectrolyte without breaking the GC plates or the seal. There was nosign of deterioration of performance due to water or non-aqueous solventpermeation through the seal and no evidence of gas build-up due toreaction of lithium with water (Li+H₂O═LiOH+½H₂) demonstrating that theseal was completely hermetic.

This is the first known example of a compliant seal enabling highlyefficient discharge of a packaged anode, which employs large amounts ofLi, into aqueous electrolyte. Also, it should be pointed out that theanode compartment, which has a compliant seal and is vacuum-filled withan interlayer electrolyte (no residual air left), contains onlyincompressible components such as Li and Ni foils and the Celgardseparator filled with non-aqueous electrolyte. Therefore, a cellemploying such anode compartment is expected to have high tolerance tolarge isostatic pressures at the depth of the ocean and to functionefficiently under these specific conditions.

Example 3 Long-Term Testing of Double-Sided Protected Lithium Anode withCompliant Seal in Aqueous Electrolyte used in Li/Air Cells

In this example, the compliant seal structure included an inorganiclayer of SnN_(x) in the bonded area of the GC surface.

Pre-Forming the MLLM

In this case, the MLLM was molded into a preformed frame. Suchpreforming allows for use of significantly thicker Li foils compared tothose used with the unformed MLLMs. Also, it ensures more uniformshrinking (collapsing) of the compliant seal during anode discharge. Onemore benefit is the potential reduction of the wasted volume of theanode compartment, depending on the frame geometry.

In the first step a square 43 mm×43 mm sheet of MLLM was molded into theshape 1 shown in FIG. 17A using a steel die and applying a pressure of500 kg. The height H was approximately 1.2 mm and the width of the topW₁ was 26 mm. The edges of the bottom step were cut, making its width W₂equal to 2 mm. The bottom opening was in a shape of a square with theside W₃ of 31 mm. A square hole of 23 mm×23 mm (W₄) with rounded corners(2.0 mm radius) was then cut in the top of the molded MLLM. As a result,a double-step frame 2 shown in FIG. 17B was formed.

Pre-Coating GC Membrane Surface with SnN_(x)

In order to achieve a strong, hermetic bond stable in aqueous andnon-aqueous electrolytes the peripheral area of the GC plate(approximately 1.7 mm wide) was coated with a thin film of SnN_(x) priorto bonding with the MLLM. The SnN_(x) films have very high chemicalresistance to acidic, neutral and basic electrolytes and to non-aqueouselectrolytes based on organic carbonates and ethers as well. The filmhad a thickness of 0.1 μm and was prepared with reactive sputtering ofmetallic tin in nitrogen plasma using the MRC 8671 sputtering unit. Thesputtered SnN_(x) film adhered to the GC membrane surface very stronglyand was well-wetted with LDPE thermoplastic layer of MLLM duringheat-sealing.

Bonding the MLLM to the GC Membrane

The next operation was bonding of the top surface of GC membrane 3 withthe bottom LDPE layer of the MLLM (see FIG. 17B) using heat-sealing. Thewidth of the seal W₅ was approximately 1.2 mm. In this case, the heatsealer employed a stainless steel resistive heating element in the formof a square frame of 26 mm×26 mm with an internal square opening of 23mm×23 mm. The Power Supply Sorensen DCS8-125E combined with a digitaltimer was used as a source of pulse voltage for heat-sealing. The designof the heat-sealer allowed us to uniformly heat the areas, where a heatseal was desired, and avoid uncontrolled softening or melting of thethermoplastic LDPE layer in other areas.

Two structures of the type shown in FIG. 17B were fabricated and thensealed together on three of their sides by bonding LDPE layers of theMLLMs' bottom steps to each other. The anode tab was fabricated asdescribed in example 2. Lithium electrode was fabricated as described inexample 2, but the Li foil from FMC Lithium Inc. had a thickness closeto 1 mm on both sides of the Ni foil current collector. Then the Lielectrode was wrapped with a 25 μm thick film of microporous Celgard3401 separator as interlayer and placed into the open-ended bag asdescribed in Example 2. The anode compartment was vacuum-filled with ananolyte solution of 1.0 M of LiClO₄ salt dissolved in propylenecarbonate, impregnating the Celgard interlayer with anolyte. The openend of the bag was then heat-sealed and the hermetic seal at thejunction between the tab and the anode compartment was ensured by theheat-seal bond. The resulting hermetically sealed anode compartment was35 mm×35 mm in size.

The protected anode architecture with compliant seal was tested in aLi/water electrochemical cell with electrolyte (catholyte) containing 3MNH₄Cl, which is used in PolyPlus Li/air batteries with protected Lianode. The electrochemical cell and setup were the same as in Example 2with the following exceptions: the glass beaker was smaller andcontained 200 ml of the aqueous electrolyte; the Ti cathode was smallerand had a geometric area of approximately 50 cm². The discharge curve atthe current density of 0.5 mA/cm² is shown in FIG. 18. The anode wasdischarged for 396 hours. The delivered capacity corresponded to 100% ofthe available capacity of Li, indicating that the seal was hermetic,since any permeation of moisture into the anode compartment would havesignificantly reduced the delivered capacity. Also, no gas evolution orbubble formation was observed during this long-term discharge. Afterdischarge, the anode was stored further in the same electrolyte(catholyte) under open circuit conditions for 53 days, resulting in thetotal time of the seal exposure to the aqueous electrolyte and thenon-aqueous interlayer electrolyte of 2.5 months. Then, the anodecompartment was removed from the aqueous electrolyte (catholyte) and thepost-mortem analysis was performed. The bond between the GC plate coatedwith SnN_(x) and the MLLM remained strong, and the laminate could not bepeeled off from the GC surface. This test demonstrates that thedouble-sided GC-protected Li anode with compliant seal and thick Li foilperforms effectively in aqueous electrolytes (catholytes) used in Li/Airbatteries. Also, it shows that the compliant seal architecture includingthe inorganic layer (SnN_(x)) in the bonded area of the GC surface isstable to aqueous (catholytes) and non-aqueous electrolytes (anolytes)in the long term.

Example 4 Long-Term Testing of Double-Sided Protected Lithium Anode withCompliant Seal in Aqueous Electrolyte (Catholyte) Used in Li/Air Cells

In this example, the area of the GC plate (solid electrolyte membrane)bonded to MLLM was etched with concentrated lithium hydroxide prior tobonding.

The anode compartment employing double-sided Li anode and two GCprotective plates (substantially impervious, ionically conductivelayers) had the same size, contained the same components (including thenon-aqueous electrolyte and two Li foils of close to 1 mm in thickness)and was fabricated the same way as in Example 3. The only difference wasthat coating with an inorganic layer was not performed. Instead, thebonded area of the GC surface was pre-treated with chemical etchingprior to bonding the GC plate to MLLM.

The peripheral area of the GC plate (approximately 1.7 mm wide) wasetched with 4M LiOH in the following way. The central area of one of thesides of the GC plate and the entire surface of the other side weremasked with Kapton tape. Then the GC plate was immersed in a beaker withan aqueous solution of 4M LiOH. After 7 days of storage the plate wasrinsed with water, then with diluted acetic acid in order to remove Licarbonate formed due to reaction of LiOH solution with atmospheric CO₂,and then again with water. Inspection of the etched GC area underoptical microscope demonstrated roughening of the surface. It should bepointed out that the duration of the surface etching could bepotentially significantly reduced by performing it at highertemperatures.

After the hermetically sealed double-sided protected anode architecturewas fabricated, it was electrochemically tested in the same cellcontaining 3M NH₄Cl as described in the previous example. The obtaineddischarge curve is shown in FIG. 19. The entire amount of Li placed inthe anode compartment was utilized during discharge. There was no signof damage to GC plates or the seal. 100% efficient discharge confirmsthat no parasitic corrosion reaction due to Li reaction with water tookplace during discharge. After discharge, the protected anode was storedfurther in the same electrolyte (catholyte) under open circuitconditions for 36 days resulting in the total time of the seal exposureto aqueous (catholyte) and non-aqueous electrolytes (anolyte) of 7.5weeks. The bond between the etched area of GC plate and the MLLMremained strong, and the laminate could not be peeled off from the GCsurface. When the anode compartment was opened, no signs of Li corrosionproducts were observed. These results show that the pre-treatment of thebonded area of the GC surface with concentrated LiOH results in ahermetic seal stable to aqueous (catholyte) and non-aqueous electrolytes(anolytes) in the long term.

Example 5 Testing of Double-Sided Protected Lithium Anode with CompliantSeal in Seawater Electrolyte

In this example, a dual sealant structure was used. The primary bondbetween the GC plate (substantially impervious, ionically conductivelayer) and the LDPE layer of MLLM was reinforced with epoxy adhesive(secondary sealant) around the heat-sealed seams.

The anode compartment employing double-sided Li anode and two GCprotective plates had the same size, contained the same components(including the non-aqueous electrolyte (anolyte) and two Li foils ofclose to 1 mm in thickness) and was fabricated the same way as inexample 3. However, coating with an inorganic layer was not performed.After the anode compartment was fabricated, epoxy adhesive Hysol E-120HPfrom Loctite Corporation was used to form the secondary seal. A fewmilliliters of Hysol E-120HP were dispensed from a 50 mL dual cartridge(Item 29353) onto a glass plate and thoroughly mixed. The central areaof GC plate was masked, and the mixed adhesive was transferred to thebonded area of the plate. The adhesive completely covered the seam ofthe primary seal. Then, the adhesive was cured at room temperature for aperiod of 20 hours. The advantage of forming the secondary seal at roomtemperature is that it does not affect temperature-sensitive componentsof the protected anode, in particular the LDPE layer of the MLLM. Theresulting hermetically sealed double-sided anode was electrochemicallytested in the same cell containing seawater electrolyte, as described inExample 2. The obtained discharge curve at a current density of 0.5mA/cm² is shown in FIG. 20. The anode was discharged for 425 hours, andthe delivered capacity corresponded to 100% of the available capacity ofLi in the anode compartment, indicating a hermetic seal. There was nodeterioration of performance due to water or non-aqueous solventpermeation through the seal. There was no evidence of gas build-up dueto reaction of Li with water. After discharge, the protected anode wasstored in the same catholyte under open circuit conditions for 10 days,resulting in the total time of the seal exposure to seawater and thenon-aqueous interlayer electrolyte (anolyte) of four weeks. When theanode was removed from the cell, the seal looked intact. No signs of Licorrosion products were observed in the opened anode compartment. Theseresults indicate that the dual seal employing the epoxy adhesive HysolE-120HP is hermetic and stable to seawater (catholyte) and non-aqueouselectrolytes (anolyte).

Example 6 Fabrication of Double-Sided Protected Lithium AnodeArchitectures Having an Asymmetric Compliant Seal Structure

A multi-layer laminate material (MLLM) manufactured by Alcan PackagingSingen GmbH (Germany) was used to make a compliant, hermetic seal to alithium ion conducting glass-ceramic (GC) membrane. In this case, aswell as in Example 7 and Example 8 described below, GC membranes wereused, developmental product AG-01, supplied to PolyPlus by OHARACorporation. The ionic conductivity of the GC membrane was 1.0×10⁻⁴S/cm. The membrane was a 1″×1″ square with a thickness of 150micrometers.

The MLLM consisted of the following layers:

-   -   PET—Polyethylene terephthalate, 48 gauge    -   ADH—a two-part polyurethane adhesive    -   Aluminum foil, 125 gauge    -   EAA—Ethacrylic acid (a primer for the aluminum foil; also        improves wetting between LDPE and PET)    -   PET—Polyethylene terephthalate, 48 gauge    -   LDPE—Low density polyethylene    -   EAA—Ethacrylic acid

The LDPE heat-sealable bottom layer served for bonding of the GCmembrane surface with the multi-layer laminate.

The compliant seal structure was formed from two component sealstructures. The first compliant seal structure component is shown inFIGS. 21A-B, and the second component shown in FIG. 21C. The first sealcomponent had a double-step pre-formed frame, and the second sealcomponent, shown in FIG. 21C, had a flat (unformed) frame.

Molding the MLLM into a Preformed Frame

In the first step a square 43 mm×43 mm sheet of MLLM was molded into theshape 1 shown in FIG. 21A using a steel die and applying a pressure of500 kg. The height H was approximately 1.6 mm and the width of the topW₁ was 26 mm. The edges of the bottom step were cut, making its width W₂equal to 2 mm. The bottom opening was in a shape of a square with theside W₃ of 31 mm. A square hole of 23 mm×23 mm (W₄) with rounded corners(2.0 mm radius) was then cut in the top of the molded MLLM. As a result,a double-step frame 2, shown in FIG. 21B, was formed.

Bonding the MLLM to the GC Membrane

The next operation was bonding of the top surface of GC membrane 3 withthe bottom LDPE layer of the preformed MLLM frame (see FIG. 21B) usingheat-sealing. The width of the seal W₅ was approximately 1.2 mm. In thiscase, the heat sealer employed a stainless steel resistive heatingelement in the form of a square frame of 26 mm×26 mm with an internalsquare opening of 23 mm×23 mm. The Power Supply Sorensen DCS8-125Ecombined with a digital timer was used as a source of pulse voltage forheat-sealing. The design of the heat-sealer allowed for uniform heatingof the areas, where a heat seal was desired, and avoid uncontrolledsoftening or melting of the thermoplastic LDPE layer in other areas.

Fabrication of Flat Frame

A square hole of 23 mm×23 mm (W₁) with rounded corners (2.0 mm radius)was cut in the top of a_square 43 mm×43 mm sheet of MLLM. As a result, aflat frame 1 shown in FIG. 21C was formed.

Bonding of the top surface of GC membrane 2 with the bottom LDPE layerof the flat MLLM frame (see FIG. 21C) was performed using heat-sealingsimilar to the operation described above for the preformed double-stepframe. The width of the seal W₂ was approximately 1.2 mm.

Lithium electrode was fabricated in the dry room by pressing two square22 mm×22 mm pieces of Li foil with a nominal thickness of 1.0 mm (FMCLithium Inc.) onto both sides of a Ni ExMet current collector having athickness of 50 μm and dimensions of 21.5 mm×21.5 mm. The pressingoperation was performed in a die with a polypropylene block using apressure of 750 kg for 3 minutes. A Ni strip with a width of 3 mm, alength of approximately 12 cm and a thickness of 50 μm served as theanode terminal tab. This tab was sandwiched between two 5 mm wide stripsof the PET film (20 μm in thickness), while both of the tab's ends wereleft exposed. The Ni foil and the PET films were sealed together with anLDPE glue. As a result, the tab was encapsulated with chemically stableand electrically insulating materials. One of tab's ends was then weldedto the Ni ExMet current collector.

The Li electrode was wrapped with a 25 μm thick film of microporousCelgard 3401 separator. Then, the Li electrode was placed between twocompliant seal structure components, shown in FIG. 20B and FIG. 20C,such that the 22 mm×22 mm Li squares were aligned with the 22 mm×22 mmareas of the GC plates not covered by the heat-seal bond with MLLM.Then, these structures were sealed together on three of their sides bybonding the LDPE layers of the flat and pre-formed frames to each other.As a result, a bag with an open end was formed.

The anode compartment was filled under vacuum with a non-aqueouselectrolyte comprising 1.0 M of LiN(CF₃SO₂)₂ salt dissolved in a mixture(1:1 by volume) of ethylene carbonate and dimethyl carbonate. Here thenon-aqueous electrolyte acted as a liquid anolyte and the anolyteimpregnated into the microporous Celgard separator, which acted as theinterlayer, separating the Li metal surface from the GC membrane. Themoisture concentration in the non-aqueous electrolyte did not exceed 10ppm.

The open end of the bag, which played a role of an anode compartmentfilling port, was then heat-sealed, and the hermetic seal at thejunction between the tab and the anode compartment was ensured by theheat-seal bond. As a result, a hermetically sealed double-sidedprotected anode architecture having an asymmetric compliant seal wasfabricated.

Example 7 Testing of Double-Sided Protected Lithium Anode HavingAsymmetric Compliant Seal in Seawater Electrolyte

The protected anode architecture with asymmetric compliant seal, thefabrication of which was described in Example 6, was tested in aLi/Water electrochemical cell with seawater electrolyte. The protectedanode architecture was completely immersed in a glass beaker containing4 L of synthetic seawater (Ricca Chemical Company). A counter electrode(cathode) was fabricated from a Ti Exmet 5Ti7-077FA in the form of acylinder with a geometrical area of 240 cm² and was placed against thewalls of the same beaker, thus surrounding the anode.

During anode discharge the Ti cathode surface facilitated the cathodicreaction of electrochemical hydrogen evolution from seawater.

The cell also employed an Ag/AgCl reference electrode, which was locatedin seawater electrolyte near the protected anode architecture and servedfor anode potential measurements during discharge. The experimentalvalues of the anode potential versus Ag/AgCl were recalculated into thestandard hydrogen electrode (SHE) scale. The anode was discharged at acurrent density of 0.5 mA/cm² of Li surface using Maccor battery tester.

The discharge curve is shown in FIG. 22. Comparison of available anodecapacity calculated from the weight of lithium foil placed in the anodecompartment and actual discharge capacity shows that discharge is 100%efficient. The entire amount of lithium was discharged from both sidesof the Ni ExMet current collector across the GC plates into seawaterelectrolyte without breaking the GC plates or the seal. The asymmetriccompliant seal structure collapsed in a uniform fashion. There was nosign of deterioration of performance due to water or non-aqueous solventpermeation through the seal and no evidence of gas build-up due toreaction of lithium with water.

Example 8 Testing of Double-Sided Protected Lithium Anode HavingAsymmetric Compliant Seal in Electrolyte of Li/Air Batteries

The protected anode architecture with asymmetric compliant sealstructure, the fabrication of which was described in Example 6, wastested in a Li/Water electrochemical cell with electrolyte containing 4MNH₄Cl, which is used in PolyPlus Li/Air batteries with protected Lianode. The electrochemical cell and setup were the same as in Example 7with the following exceptions: the glass beaker was smaller andcontained 200 ml of the aqueous electrolyte; the Ti cathode was smallerand had a geometric area of approximately 50 cm². The discharge curve atthe current density of 1.0 mA/cm² is shown in FIG. 23. It was observedthat the asymmetric seal collapsed in a uniform fashion. The deliveredcapacity corresponded to 100% of the available capacity of Li,indicating that the seal was hermetic, since any permeation of moistureinto the anode compartment would have significantly reduced thedelivered capacity. Also, no gas evolution or bubble formation wasobserved during this long-term discharge.

The results described in Examples 7 and 8 have demonstrated theeffectiveness of a protected anode architecture employing an asymmetriccompliant seal structure in Li/Water and Li/Air batteries.

In conclusion, the results described in Examples 1-8 have experimentallyproved the concept of compliant seal structures and have demonstratedthe effectiveness of protected anode architectures employing such sealsin Li/Water and Li/Air batteries.

CONCLUSION

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theinvention. While the invention has been described in conjunction withsome specific embodiments, it will be understood that it is not intendedto limit the invention to such specific embodiments. On the contrary, itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as definedherein.

All references cited herein are incorporated by reference for allpurposes.

1. A protected anode architecture having a predefined lower boundoperating temperature, the architecture comprising: an active metalanode having a first surface and a second surface; an ionicallyconductive protective membrane architecture in physical continuity withthe first surface of the anode; an active metal anode backplane inphysical continuity with the second surface of the anode; and acompliant seal structure comprising a flexible multilayer laminatehaving a top and a bottom thermoplastic material layer each having aglass transition temperature, the seal structure interfacing with theprotective membrane architecture and the anode backplane to enclose theanode in an anode compartment, the seal structure being compliant tochanges in anode thickness such that physical continuity between theanode, protective architecture and backplane are maintained; wherein theionically conductive protective membrane architecture comprises one ormore materials configured to provide a first membrane surface chemicallycompatible with the active metal of the anode in contact with the anode,and a second membrane surface substantially impervious to and chemicallycompatible with an environment exterior to the anode compartment;wherein the seal structure interfaces with the protective membranearchitecture and the anode backplane such that a substantiallyimpervious barrier between the interior and exterior of the anodecompartment is provided; and further wherein the glass transitiontemperature of both the top and bottom layer is lower than thepredefined lower bound operating temperature of the protected anodearchitecture.
 2. The protected anode architecture of claim 1, wherein nothermoplastic material layer having a thickness greater than that of oneof the group consisting of 200, 100, 50, 20, 10 and 5 microns has aglass transition temperature above the low operating temperature limitof the protected anode architecture.
 3. The protected anode architectureof claim 1 wherein the predefined lower bound operating temperature ofthe protected anode architecture or of a battery in which it isincorporated is selected from the group consisting of 15° C., 10° C., 5°C., 0° C., −5° C., −10° C., −20° C., and −40° C.
 4. A protected anodearchitecture comprising: an active metal anode having a first surfaceand a second surface; an ionically conductive protective membranearchitecture in physical continuity with the first surface of the anode;an active metal anode backplane in physical continuity with the secondsurface of the anode; and a compliant seal structure comprising aflexible multilayer laminate having a top and a bottom thermoplasticmaterial layer each having a glass transition temperature, the sealstructure interfacing with the protective membrane architecture and theanode backplane to enclose the anode in an anode compartment, the sealstructure being compliant to changes in anode thickness such thatphysical continuity between the anode, protective architecture andbackplane are maintained; wherein the ionically conductive protectivemembrane architecture comprises one or more materials configured toprovide a first membrane surface chemically compatible with the activemetal of the anode in contact with the anode, and a second membranesurface substantially impervious to and chemically compatible with anenvironment exterior to the anode compartment; wherein the sealstructure interfaces with the protective membrane architecture and theanode backplane such that a substantially impervious barrier between theinterior and exterior of the anode compartment is provided; and furtherwherein the glass transition temperature of both the top and bottomlayer is less than a temperature selected from the group consisting of15° C., 10° C., 5° C., 0° C., −5° C., −10° C., −20° C., and −40° C. 5.The protected anode architecture of claim 4, wherein no thermoplasticmaterial layer having a thickness greater than that of one of the groupconsisting of 200, 100, 50, 20, 10 and 5 microns has a glass transitiontemperature above a temperature selected from the group consisting of15° C., 10° C., 5° C., 0° C., −5° C., −10° C., −20° C., and −40° C.
 6. Aprotected anode architecture comprising: an active metal anode having afirst surface and a second surface; an ionically conductive protectivemembrane architecture in physical continuity with the first surface ofthe anode; an active metal anode backplane in physical continuity withthe second surface of the anode; and a compliant seal structurecomprising a flexible multilayer laminate having a top and a bottomthermoplastic material layer, the seal structure interfacing with theprotective membrane architecture and the anode backplane to enclose theanode in an anode compartment, the seal structure being compliant tochanges in anode thickness such that physical continuity between theanode, protective architecture and backplane are maintained; wherein theionically conductive protective membrane architecture comprises one ormore materials configured to provide a first membrane surface chemicallycompatible with the active metal of the anode in contact with the anode,and a second membrane surface substantially impervious to and chemicallycompatible with an environment exterior to the anode compartment;wherein the seal structure interfaces with the protective membranearchitecture and the anode backplane such that a substantiallyimpervious barrier between the interior and exterior of the anodecompartment is provided; and further wherein the melt temperature of thetop layer is greater than that of the bottom layer.
 7. The protectedanode architecture of claim 6, wherein the top layer is polypropylenelayer, for example oriented polypropylene (OPP)
 8. The protected anodearchitecture of claim 6, wherein the bottom layer is an integratedsealant layer for providing a primary heat seal bond to the protectivemembrane architecture.
 9. The protected anode architecture of claim 8,wherein the bottom layer is an acidic copolymer.
 10. The protected anodearchitecture of claim 9, wherein the bottom layer is ethylene acrylicacid (EAA) copolymer.
 11. The protected anode architecture of claim 6,wherein the laminate further comprises a metal foil inner layerinterposed between the top and bottom layers.
 12. The protected anodearchitecture of claim 11, wherein the metal foil inner layer is analuminum alloy.
 13. The protected anode architecture of claim 6, whereinthe multilayer laminate further comprises an additional inner layer, anintegrated secondary sealant layer that serves the purpose of providinga secondary seal that protects the laminate edge.
 14. The protectedanode architecture of claim 13, wherein the secondary seal forms acoating, by extrusion, over the exposed portion of the bottom layer atthe laminate edge, the extrusion coating extending onto the surface ofprotective membrane architecture.
 15. The protected anode architectureof claim 6, further comprising a discrete sealant covering the edge ofthe bottom layer.
 16. The protected anode architecture of claim 15,wherein the discrete sealant is a thermoplastic strip.
 17. The protectedanode architecture of claim 6, wherein the laminate further comprises ametal foil barrier layer interposed between the top and bottom layersand a secondary integrated sealant layer interposed between the metalfoil layer and the top layer.
 18. The protected anode architecture ofclaim 17 wherein the top material layer is polypropylene, the bottomheat sealable material layer is EAA, the metal barrier layer is analuminum alloy.
 19. A battery cell comprising: a protected anodearchitecture in accordance with claim 1, and further comprising acathode structure.
 20. The battery cell of claim 19, wherein the cathodestructure comprises seawater as an electrochemically active component,and the battery cell is a lithium seawater battery.
 21. The battery cellof claim 19, wherein the cathode structure comprises molecular oxygen asan electrochemically active component.
 22. The battery cell of claim 21,wherein the electrochemically active component is ambient air.